diff --git a/changelog.d/hi-ccap-copay-income-base.fixed.md b/changelog.d/hi-ccap-copay-income-base.fixed.md
new file mode 100644
index 00000000000..0b4715a8f14
--- /dev/null
+++ b/changelog.d/hi-ccap-copay-income-base.fixed.md
@@ -0,0 +1 @@
+Hawaii CCAP co-payments follow HAR 17-798.3-14 beginning August 2021, applying the sliding-scale tier to the family's monthly gross income; the prior HAR 17-798.2-14(b)(4) provider-rate method is preserved for earlier periods.
diff --git a/policyengine_us/parameters/gov/states/hi/bessd/ccap/copay/income_based_in_effect.yaml b/policyengine_us/parameters/gov/states/hi/bessd/ccap/copay/income_based_in_effect.yaml
new file mode 100644
index 00000000000..2c0edfb3545
--- /dev/null
+++ b/policyengine_us/parameters/gov/states/hi/bessd/ccap/copay/income_based_in_effect.yaml
@@ -0,0 +1,24 @@
+description: Hawaii computes the Child Care Subsidy co-payment as a percentage of the family's monthly gross income when this is in effect, and as a percentage of the department's maximum rate allowable otherwise.
+
+values:
+  2020-01-01: false
+  2021-08-06: true
+
+metadata:
+  unit: bool
+  period: year
+  label: Hawaii CCAP income-based co-payment in effect
+  reference:
+    # HAR chapter 17-798.3 (effective August 6, 2021) replaced the
+    # payment provisions of chapter 17-798.2; its section -14 multiplies
+    # the co-payment tier by the family unit's monthly gross income,
+    # where the superseded 17-798.2-14(b)(4) multiplied it by the
+    # department's maximum rate allowable. Monthly formulas read this
+    # parameter as of the first day of the month, so the model applies
+    # the income-based method from September 2021 onward; August 2021,
+    # which straddles the effective date, still uses the maximum-rate
+    # method.
+    - title: HAR 17-798.3-14, co-payment tier multiplied by the family unit's monthly gross income (eff. 2021-08-06)
+      href: https://humanservices.hawaii.gov/bessd/files/2021/09/CHAPTER-17-798.3-Child-Care-Payments.pdf#page=35
+    - title: HAR 17-798.2-14(b)(4), co-payment tier multiplied by the department's maximum rate allowable (superseded)
+      href: https://humanservices.hawaii.gov/bessd/files/2013/01/HAR-17-798.2-Child-Care-Services-Rules.pdf#page=29
diff --git a/policyengine_us/parameters/gov/states/hi/bessd/ccap/copay/rate.yaml b/policyengine_us/parameters/gov/states/hi/bessd/ccap/copay/rate.yaml
index eb0279788f9..836c0bb1322 100644
--- a/policyengine_us/parameters/gov/states/hi/bessd/ccap/copay/rate.yaml
+++ b/policyengine_us/parameters/gov/states/hi/bessd/ccap/copay/rate.yaml
@@ -1,4 +1,4 @@
-description: Hawaii sets this co-payment percentage of the department's maximum rate allowable under the Child Care Subsidy program, by the family's gross income as a share of the federal poverty guidelines.
+description: Hawaii sets this co-payment percentage under the Child Care Subsidy program, by the family's gross income as a share of the federal poverty guidelines.
 
 metadata:
   type: single_amount
@@ -7,18 +7,18 @@ metadata:
   period: year
   label: Hawaii CCAP co-payment rate by FPG ratio
   reference:
-    # HAR 17-798.2-14(b)(4): co-payment = (percentage of the department's
-    # maximum rate allowable) based on the family's monthly gross income.
-    # The rule's attached scale is "Exhibit III (dated Oct 1, 2009)", which has
-    # been superseded by the 2020 sliding-fee scale below; the implemented
-    # 0-9% percentages come from that 2020 scale, the operative source.
-    - title: HAR 17-798.2-14(b)(4)
-      href: https://humanservices.hawaii.gov/bessd/files/2013/01/HAR-17-798.2-Child-Care-Services-Rules.pdf#page=29
-    # Operative sliding fee scale (single-page scanned chart, eff 2020-01-02)
-    # mapping each FPG band to its co-payment percentage. The standalone PDF
-    # labels itself "Exhibit II" in its own footer, which is its internal
-    # numbering and differs from the HAR's exhibit numbering (Exhibit III).
-    - title: Hawaii DHS Child Care Gross Income Eligibility Limits and Sliding Fee Scale (PDF "Exhibit II"), effective 2020-01-02
+    # HAR 17-798.3-14(3) (eff. 2021-08-06, page 35 of the chapter PDF)
+    # determines the co-payment tier from Exhibit II, dated January 2,
+    # 2020, attached at the end of the chapter; step (4) multiplies the
+    # tier by the family unit's monthly gross income. The percentages
+    # below are the Exhibit II column headings. The superseded
+    # 17-798.2-14(b)(4) used the same tier scale but multiplied it by the
+    # department's maximum rate allowable (see income_based_in_effect.yaml).
+    - title: HAR 17-798.3, Exhibit II Child Care Gross Income Eligibility Limits and Sliding Fee Scale (dated January 2, 2020), applied under 17-798.3-14(3) (tier selection; the multiply is step (4))
+      href: https://humanservices.hawaii.gov/bessd/files/2021/09/CHAPTER-17-798.3-Child-Care-Payments.pdf#page=73
+    # The same Exhibit II scale as a standalone scanned chart (eff
+    # 2020-01-02), mapping each FPG band to its co-payment percentage.
+    - title: Hawaii DHS Child Care Gross Income Eligibility Limits and Sliding Fee Scale (Exhibit II), effective 2020-01-02
       href: https://childcaresubsidyapplication.dhs.hawaii.gov/Child-Care-Gross-Income-Eligibility-Limits-and-Sliding-Fee-Scale
 
 # Bands are "above X%" boundaries (e.g., 101-115% means above 100% up to
diff --git a/policyengine_us/parameters/gov/states/hi/bessd/ccap/income/countable_income/sources.yaml b/policyengine_us/parameters/gov/states/hi/bessd/ccap/income/countable_income/sources.yaml
index 557192dc00c..63eaaa2b789 100644
--- a/policyengine_us/parameters/gov/states/hi/bessd/ccap/income/countable_income/sources.yaml
+++ b/policyengine_us/parameters/gov/states/hi/bessd/ccap/income/countable_income/sources.yaml
@@ -48,6 +48,12 @@ metadata:
   period: year
   label: Hawaii CCAP countable income sources
   reference:
+    # Chapter 17-798.3 (eff. 2021-08-06) carries the same source list in
+    # 17-798.3-10(b) and the same exclusions in 17-798.3-11 (page 29);
+    # "gross income" is defined in 17-798.3-2 as all non-excluded earned
+    # and unearned income.
+    - title: HAR 17-798.3-10(b) and 17-798.3-11
+      href: https://humanservices.hawaii.gov/bessd/files/2021/09/CHAPTER-17-798.3-Child-Care-Payments.pdf#page=24
     - title: HAR 17-798.2-10(b)
       href: https://humanservices.hawaii.gov/bessd/files/2013/01/HAR-17-798.2-Child-Care-Services-Rules.pdf#page=19
     - title: HAR 17-798.2-11
diff --git a/policyengine_us/tests/policy/baseline/gov/states/hi/bessd/ccap/copay/hi_ccap_copay.yaml b/policyengine_us/tests/policy/baseline/gov/states/hi/bessd/ccap/copay/hi_ccap_copay.yaml
index 075e1ca3314..65ff2be8a04 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/hi/bessd/ccap/copay/hi_ccap_copay.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/hi/bessd/ccap/copay/hi_ccap_copay.yaml
@@ -1,12 +1,11 @@
-# HI CCAP family co-payment (HAR 17-798.2-14(b)(4)).
-# Co-payment = (department's maximum rate allowable) x (co-pay percentage).
-# The percentage multiplies the PROVIDER MAX RATE, not gross income. This is
-# the HI-specific difference from income-times-percent designs.
+# HI CCAP family co-payment (HAR 17-798.3-14, eff. 2021-08-06).
+# Co-payment = (co-payment tier from Exhibit II) x (monthly gross income
+# for the family unit), assessed once per family unit.
 #
 # Family of 2, HI 2025 (FPG family of 2 = 24,320/year = 2,026.67/month).
 # Children are full-time (childcare_hours_per_week 30 -> ~130 monthly hours).
 
-- name: Case 1, worked example 740 rate times 9 percent.
+- name: Case 1, worked example gross income times 9 percent.
   period: 2025-01
   absolute_error_margin: 0.01
   input:
@@ -31,11 +30,11 @@
         members: [person1, person2]
         state_code: HI
   output:
-    # Max rate (licensed center or group home, full-time) = 795; copay rate 9%
-    # copay = 795 x 0.09 = 71.55
-    hi_ccap_copay: 71.55
+    # Monthly gross income = 56,000 / 12 = 4,666.67; copay tier 9%
+    # copay = 4,666.67 x 0.09 = 420.00
+    hi_ccap_copay: 420
 
-- name: Case 2, infant/toddler rate 1733 times 5 percent.
+- name: Case 2, gross income times 5 percent.
   period: 2025-01
   absolute_error_margin: 0.01
   input:
@@ -60,9 +59,9 @@
         members: [person1, person2]
         state_code: HI
   output:
-    # Max rate (licensed center infant/toddler, full-time) = 1,733; copay rate 5%
-    # copay = 1,733 x 0.05 = 86.65
-    hi_ccap_copay: 86.65
+    # Monthly gross income = 40,800 / 12 = 3,400; copay tier 5%
+    # copay = 3,400 x 0.05 = 170.00 (the provider rate does not enter)
+    hi_ccap_copay: 170
 
 - name: Case 3, zero copay percent gives zero copay.
   period: 2025-01
@@ -89,5 +88,214 @@
         members: [person1, person2]
         state_code: HI
   output:
-    # 795 x 0.00 = 0
+    # 1,000 x 0.00 = 0
     hi_ccap_copay: 0
+
+# The FFY2025-2027 CCDF plan (section 3.1.2) shows a family unit of 1 at
+# monthly income 3,632 paying a 327 co-payment: ratio far above 230% FPG
+# -> 9% tier, and 3,632 x 0.09 = 326.88, which rounds to the plan's 327.
+- name: Case 4, CCDF plan worked example, family of 1 at 3632 per month.
+  period: 2025-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 25
+        employment_income: 43_584  # 3,632/mo
+        immigration_status: CITIZEN
+    tax_units:
+      tax_unit:
+        members: [person1]
+    spm_units:
+      spm_unit:
+        members: [person1]
+    households:
+      household:
+        members: [person1]
+        state_code: HI
+  output:
+    hi_ccap_copay_rate: 0.09
+    hi_ccap_copay: 326.88
+
+# === Effective-date boundary: HAR 17-798.3 replaced 17-798.2's payment
+# provisions on August 6, 2021. Before then the co-payment was the tier
+# percentage of the department's maximum rate allowable, per child
+# (17-798.2-14(b)(4)); since then it is the tier percentage of monthly
+# gross income, per family unit (17-798.3-14). ===
+
+- name: Case 5, before August 2021 the tier applies to the provider maximum rate.
+  period: 2021-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 30
+        employment_income: 56_000  # 4,666.67/mo, far above 230% FPG -> 9%
+        immigration_status: CITIZEN
+      person2:
+        age: 4
+        immigration_status: CITIZEN
+        childcare_hours_per_week: 30
+        hi_ccap_provider_category: LICENSED_CENTER_OR_GROUP_HOME
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+    spm_units:
+      spm_unit:
+        members: [person1, person2]
+    households:
+      household:
+        members: [person1, person2]
+        state_code: HI
+  output:
+    # Max rate (licensed center or group home, full-time) = 795
+    # copay = 795 x 0.09 = 71.55
+    hi_ccap_copay: 71.55
+
+- name: Case 6, from the 2021 rule change the tier applies to gross income.
+  period: 2022-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 30
+        employment_income: 56_000  # 4,666.67/mo, far above 230% FPG -> 9%
+        immigration_status: CITIZEN
+      person2:
+        age: 4
+        immigration_status: CITIZEN
+        childcare_hours_per_week: 30
+        hi_ccap_provider_category: LICENSED_CENTER_OR_GROUP_HOME
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+    spm_units:
+      spm_unit:
+        members: [person1, person2]
+    households:
+      household:
+        members: [person1, person2]
+        state_code: HI
+  output:
+    # copay = 4,666.67 x 0.09 = 420.00 (same household as Case 5)
+    hi_ccap_copay: 420
+
+# The August 6, 2021 effective date falls mid-month. Monthly formulas read
+# income_based_in_effect as of the first day of the month, so August 2021
+# is the last month on the maximum-rate method and September 2021 the
+# first on the gross-income method. HI 2021 FPG family of 2 =
+# 20,040/year = 1,670/month, so 4,666.67 is 2.79 x FPG -> 9% tier.
+
+- name: Case 7, August 2021 still uses the maximum-rate method and September 2021 is the first month on the gross-income method.
+  period: 2021
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 30
+        employment_income: 56_000  # 4,666.67/mo, FPG ratio 2.79 -> 9%
+        immigration_status: CITIZEN
+      person2:
+        age: 4
+        immigration_status: CITIZEN
+        childcare_hours_per_week: 30
+        hi_ccap_provider_category: LICENSED_CENTER_OR_GROUP_HOME
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+    spm_units:
+      spm_unit:
+        members: [person1, person2]
+    households:
+      household:
+        members: [person1, person2]
+        state_code: HI
+  output:
+    # The toggle is still false on August 1, 2021 and true on September 1:
+    # August copay = 795 (max rate) x 0.09 = 71.55
+    # September copay = 4,666.67 (gross income) x 0.09 = 420.00
+    hi_ccap_copay_rate:
+      2021-08: 0.09
+      2021-09: 0.09
+    hi_ccap_copay:
+      2021-08: 71.55
+      2021-09: 420
+
+# Two children in care: the old method summed each child's maximum rate
+# before applying the tier; the new method charges the tier on the family's
+# income once, regardless of how many children are in care. Family of 3,
+# 66,000/year = 5,500/month. HI FPG family of 3: 2021 = 25,260/year =
+# 2,105/month (ratio 2.61); 2022 = 26,490/year = 2,207.50/month
+# (ratio 2.49). Both years land in the 9% tier.
+
+- name: Case 8, before August 2021 two children sum their maximum rates.
+  period: 2021-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 30
+        employment_income: 66_000  # 5,500/mo, FPG ratio 2.61 -> 9%
+        immigration_status: CITIZEN
+      person2:
+        age: 1  # < 36 months -> INFANT_TODDLER rate
+        immigration_status: CITIZEN
+        childcare_hours_per_week: 30
+        hi_ccap_provider_category: LICENSED_CENTER_OR_GROUP_HOME
+      person3:
+        age: 4  # >= 36 months -> OLDER rate
+        immigration_status: CITIZEN
+        childcare_hours_per_week: 30
+        hi_ccap_provider_category: LICENSED_CENTER_OR_GROUP_HOME
+    tax_units:
+      tax_unit:
+        members: [person1, person2, person3]
+    spm_units:
+      spm_unit:
+        members: [person1, person2, person3]
+    households:
+      household:
+        members: [person1, person2, person3]
+        state_code: HI
+  output:
+    # Licensed center full-time rates: infant/toddler 1,733 + older 795
+    # = 2,528; copay = 2,528 x 0.09 = 227.52
+    hi_ccap_maximum_monthly_rate: [0, 1_733, 795]
+    hi_ccap_copay_rate: 0.09
+    hi_ccap_copay: 227.52
+
+- name: Case 9, from the 2021 rule change two children still pay the tier on income once.
+  period: 2022-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 30
+        employment_income: 66_000  # 5,500/mo, FPG ratio 2.49 -> 9%
+        immigration_status: CITIZEN
+      person2:
+        age: 1  # < 36 months -> INFANT_TODDLER rate
+        immigration_status: CITIZEN
+        childcare_hours_per_week: 30
+        hi_ccap_provider_category: LICENSED_CENTER_OR_GROUP_HOME
+      person3:
+        age: 4  # >= 36 months -> OLDER rate
+        immigration_status: CITIZEN
+        childcare_hours_per_week: 30
+        hi_ccap_provider_category: LICENSED_CENTER_OR_GROUP_HOME
+    tax_units:
+      tax_unit:
+        members: [person1, person2, person3]
+    spm_units:
+      spm_unit:
+        members: [person1, person2, person3]
+    households:
+      household:
+        members: [person1, person2, person3]
+        state_code: HI
+  output:
+    # Same household and rates as Case 8, but the rates no longer enter:
+    # copay = 5,500 (gross income) x 0.09 = 495.00, not 227.52
+    hi_ccap_maximum_monthly_rate: [0, 1_733, 795]
+    hi_ccap_copay_rate: 0.09
+    hi_ccap_copay: 495
diff --git a/policyengine_us/tests/policy/baseline/gov/states/hi/bessd/ccap/copay/hi_ccap_copay_rate.yaml b/policyengine_us/tests/policy/baseline/gov/states/hi/bessd/ccap/copay/hi_ccap_copay_rate.yaml
index 2804c50bc36..8906ff01a9c 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/hi/bessd/ccap/copay/hi_ccap_copay_rate.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/hi/bessd/ccap/copay/hi_ccap_copay_rate.yaml
@@ -1,4 +1,4 @@
-# HI CCAP co-payment rate by FPG band (Exhibit II, HAR 17-798.2-14(b)(4)).
+# HI CCAP co-payment rate by FPG band (Exhibit II, HAR 17-798.3-14(3)).
 # The rate is a function of monthly gross income as a share of the federal
 # poverty guidelines, independent of family size. Bands (income above X%):
 #   0-100% -> 0%, 101-115% -> 1%, 116-130% -> 2%, 131-145% -> 3%,
diff --git a/policyengine_us/tests/policy/baseline/gov/states/hi/bessd/ccap/hi_ccap.yaml b/policyengine_us/tests/policy/baseline/gov/states/hi/bessd/ccap/hi_ccap.yaml
index 215beaadb7f..6ed40870741 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/hi/bessd/ccap/hi_ccap.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/hi/bessd/ccap/hi_ccap.yaml
@@ -94,9 +94,9 @@
         members: [person1, person2]
         state_code: HI
   output:
-    # capped = min(1,000, 795) = 795; copay = 795 x 0.09 = 71.55
-    # subsidy = 795 - 71.55 = 723.45
-    hi_ccap: 723.45
+    # capped = min(1,000, 795) = 795; copay = 4,666.67 x 0.09 = 420.00
+    # subsidy = 795 - 420.00 = 375.00
+    hi_ccap: 375
 
 - name: Case 4, two children sum their rates.
   period: 2025-01
@@ -230,9 +230,9 @@
         state_code: HI
   output:
     # capped = min(500 charge, 795 rate) = 500
-    # copay = 795 x 0.09 = 71.55 (always on the dept max rate)
-    # subsidy = max(500 - 71.55, 0) = 428.45 (lesser is the charge, not rate)
-    hi_ccap: 428.45
+    # copay = 4,666.67 x 0.09 = 420.00 (on gross income)
+    # subsidy = max(500 - 420.00, 0) = 80.00 (lesser is the charge, not rate)
+    hi_ccap: 80
 
 - name: Case 8, copay larger than the lesser-of amount floors the subsidy at zero.
   period: 2025-01
@@ -262,8 +262,8 @@
         members: [person1, person2]
         state_code: HI
   output:
-    # capped = min(1 charge, 795 rate) = 1; copay = 795 x 0.09 = 71.55
-    # subsidy = max(1 - 71.55, 0) = 0 (no negative benefit)
+    # capped = min(1 charge, 795 rate) = 1; copay = 4,666.67 x 0.09 = 420.00
+    # subsidy = max(1 - 420.00, 0) = 0 (no negative benefit)
     hi_ccap: 0
 
 - name: Case 9, household with no children produces a graceful zero.
@@ -401,3 +401,44 @@
     hi_ccap_maximum_monthly_rate: [0, 86]
     # subsidy = min(1,000 expenses, 86 rate) - 0 copay = 86
     hi_ccap: 86
+
+# === Pre-August-2021 co-payment method (HAR 17-798.2-14(b)(4)) ===
+
+- name: Case 13, before August 2021 the copay on the maximum rate reduces the subsidy.
+  period: 2021-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 30
+        employment_income: 56_000  # 4,666.67/mo
+        weekly_hours_worked_before_lsr: 40
+        immigration_status: CITIZEN
+      person2:
+        age: 4
+        immigration_status: CITIZEN
+        is_in_k12_school: false
+        childcare_hours_per_week: 30
+        hi_ccap_provider_category: LICENSED_CENTER_OR_GROUP_HOME
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+    spm_units:
+      spm_unit:
+        members: [person1, person2]
+        spm_unit_pre_subsidy_childcare_expenses: 12_000  # 1,000/mo
+    households:
+      household:
+        members: [person1, person2]
+        state_code: HI
+  output:
+    # 2021: HI SMI 104,242 x 0.68 (family of 2) x 0.85 / 12 = 5,020.99
+    # >= 4,666.67 -> income eligible; FPG family of 2 = 1,670/mo, ratio
+    # 2.79 -> 9%.
+    hi_ccap_eligible: true
+    # Same household as Case 3, but the copay is 9% of the 795 maximum
+    # rate rather than of income: 795 x 0.09 = 71.55.
+    hi_ccap_copay: 71.55
+    # capped = min(1,000, 795) = 795; subsidy = 795 - 71.55 = 723.45
+    # (versus 375 under the gross-income method in Case 3)
+    hi_ccap: 723.45
diff --git a/policyengine_us/tests/policy/baseline/gov/states/hi/bessd/ccap/integration.yaml b/policyengine_us/tests/policy/baseline/gov/states/hi/bessd/ccap/integration.yaml
index 04817f4602f..3177adf0c2c 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/hi/bessd/ccap/integration.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/hi/bessd/ccap/integration.yaml
@@ -96,10 +96,10 @@
     hi_ccap_maximum_monthly_rate: [0, 795]
     # FPG ratio = 5,000 / 2,026.67 = 2.4671 -> 9% band
     hi_ccap_copay_rate: 0.09
-    # copay = 795 x 0.09 = 71.55
-    hi_ccap_copay: 71.55
-    # capped = min(1,000 expenses, 795 rate) = 795; subsidy = 795 - 71.55
-    hi_ccap: 723.45
+    # copay = 5,000 x 0.09 = 450.00
+    hi_ccap_copay: 450
+    # capped = min(1,000 expenses, 795 rate) = 795; subsidy = 795 - 450.00
+    hi_ccap: 345
 
 - name: Case 3, protective-services child with income test waived.
   period: 2025-01
@@ -139,10 +139,11 @@
     hi_ccap_maximum_monthly_rate: [0, 980]
     # FPG ratio far above 230% -> 9% band
     hi_ccap_copay_rate: 0.09
-    # copay = 980 x 0.09 = 88.20
-    hi_ccap_copay: 88.20
-    # capped = min(1,000, 980) = 980; subsidy = 980 - 88.20
-    hi_ccap: 891.80
+    # copay = 16,666.67 x 0.09 = 1,500.00 (scales with income, so the
+    # high-income family owes more than the capped rate)
+    hi_ccap_copay: 1_500
+    # capped = min(1,000, 980) = 980; subsidy = max(980 - 1,500, 0) = 0
+    hi_ccap: 0
 
 - name: Case 4, disabled teenager in before-after-school care.
   period: 2025-01
@@ -184,10 +185,10 @@
     hi_ccap_maximum_monthly_rate: [0, 155]
     # FPG ratio = 2,500 / 2,026.67 = 1.2336 -> 2% band
     hi_ccap_copay_rate: 0.02
-    # copay = 155 x 0.02 = 3.10
-    hi_ccap_copay: 3.10
-    # capped = min(250 expenses, 155 rate) = 155; subsidy = 155 - 3.10
-    hi_ccap: 151.90
+    # copay = 2,500 x 0.02 = 50.00
+    hi_ccap_copay: 50
+    # capped = min(250 expenses, 155 rate) = 155; subsidy = 155 - 50.00
+    hi_ccap: 105
 
 - name: Case 5, two children at different provider types.
   period: 2025-01
@@ -235,10 +236,11 @@
     # FPG family of 3 = 30,650/yr = 2,554.17/mo
     # ratio = 3,000 / 2,554.17 = 1.1746 -> 2% band
     hi_ccap_copay_rate: 0.02
-    # copay = (400 + 86) x 0.02 = 9.72
-    hi_ccap_copay: 9.72
-    # capped = min(750 expenses, 486 rates) = 486; subsidy = 486 - 9.72
-    hi_ccap: 476.28
+    # copay = 3,000 x 0.02 = 60.00, assessed once per family unit
+    # regardless of the number of children in care
+    hi_ccap_copay: 60
+    # capped = min(750 expenses, 486 rates) = 486; subsidy = 486 - 60.00
+    hi_ccap: 426
 
 - name: Case 6, two-parent family with one idle parent is ineligible.
   period: 2025-01
diff --git a/policyengine_us/variables/gov/states/hi/bessd/ccap/copay/hi_ccap_copay.py b/policyengine_us/variables/gov/states/hi/bessd/ccap/copay/hi_ccap_copay.py
index 36c906eed74..67bbe0e0c6e 100644
--- a/policyengine_us/variables/gov/states/hi/bessd/ccap/copay/hi_ccap_copay.py
+++ b/policyengine_us/variables/gov/states/hi/bessd/ccap/copay/hi_ccap_copay.py
@@ -8,12 +8,29 @@ class hi_ccap_copay(Variable):
     label = "Hawaii CCAP family co-payment"
     definition_period = MONTH
     defined_for = StateCode.HI
-    reference = "https://humanservices.hawaii.gov/bessd/files/2013/01/HAR-17-798.2-Child-Care-Services-Rules.pdf#page=29"
+    reference = (
+        "https://humanservices.hawaii.gov/bessd/files/2021/09/CHAPTER-17-798.3-Child-Care-Payments.pdf#page=35",
+        "https://humanservices.hawaii.gov/bessd/files/2013/01/HAR-17-798.2-Child-Care-Services-Rules.pdf#page=29",
+    )
 
     def formula(spm_unit, period, parameters):
-        # Co-payment = (department's maximum rate allowable) x (co-payment
-        # percentage from the sliding fee scale) (HAR 17-798.2-14(b)(4)).
-        # The percentage multiplies the provider max rate, not gross income.
-        maximum_monthly_rate = add(spm_unit, period, ["hi_ccap_maximum_monthly_rate"])
+        p = parameters(period).gov.states.hi.bessd.ccap.copay
         copay_rate = spm_unit("hi_ccap_copay_rate", period)
-        return maximum_monthly_rate * copay_rate
+        # From August 6, 2021, the co-payment is the sliding-fee tier
+        # multiplied by the family unit's monthly gross income, assessed
+        # once per family (HAR 17-798.3-14(4); the tier itself is selected
+        # at step (3)). Before then, it was the tier multiplied by the
+        # department's maximum rate allowable, per child in care
+        # (HAR 17-798.2-14(b)(4)).
+        # "Gross income" is a defined term in both chapters: "all
+        # non-excluded earned and unearned income as specified in this
+        # chapter" (HAR 17-798.3-2; identically HAR 17-798.2-2). The
+        # counted sources are listed in 17-798.3-10(b) and the exclusions,
+        # including the 17-798.3-11(8) earnings of minor children who are
+        # at least half-time students, in 17-798.3-11 (mirroring
+        # 17-798.2-10 and -11). The statutory monthly gross income is
+        # therefore the same countable income that selects the tier.
+        countable_income = spm_unit("hi_ccap_countable_income", period)
+        maximum_monthly_rate = add(spm_unit, period, ["hi_ccap_maximum_monthly_rate"])
+        base = where(p.income_based_in_effect, countable_income, maximum_monthly_rate)
+        return base * copay_rate
diff --git a/policyengine_us/variables/gov/states/hi/bessd/ccap/copay/hi_ccap_copay_rate.py b/policyengine_us/variables/gov/states/hi/bessd/ccap/copay/hi_ccap_copay_rate.py
index 05cb287dee9..4e8470cbce6 100644
--- a/policyengine_us/variables/gov/states/hi/bessd/ccap/copay/hi_ccap_copay_rate.py
+++ b/policyengine_us/variables/gov/states/hi/bessd/ccap/copay/hi_ccap_copay_rate.py
@@ -7,15 +7,15 @@ class hi_ccap_copay_rate(Variable):
     label = "Hawaii CCAP co-payment rate"
     definition_period = MONTH
     defined_for = StateCode.HI
-    reference = "https://humanservices.hawaii.gov/bessd/files/2013/01/HAR-17-798.2-Child-Care-Services-Rules.pdf#page=29"
+    reference = "https://humanservices.hawaii.gov/bessd/files/2021/09/CHAPTER-17-798.3-Child-Care-Payments.pdf#page=35"
 
     def formula(spm_unit, period, parameters):
         p = parameters(period).gov.states.hi.bessd.ccap.copay
         countable_income = spm_unit("hi_ccap_countable_income", period)
         fpg = spm_unit("spm_unit_fpg", period)
-        # Co-payment percentage is a function of the family's gross income
-        # as a share of the federal poverty guidelines (HAR
-        # 17-798.2-14(b)(4); Exhibit II sliding fee scale). The dollar
+        # The co-payment tier is a function of the family's gross income
+        # as a share of the federal poverty guidelines (HAR 17-798.3-14(3);
+        # Exhibit II sliding fee scale, dated January 2, 2020). The dollar
         # columns in Exhibit II are just FPG x band, so the percentage is
         # independent of family size.
         fpg_ratio = where(fpg > 0, countable_income / fpg, 0)
diff --git a/policyengine_us/variables/gov/states/hi/bessd/ccap/hi_ccap_countable_income.py b/policyengine_us/variables/gov/states/hi/bessd/ccap/hi_ccap_countable_income.py
index 691d83703ef..c38c3cd56e0 100644
--- a/policyengine_us/variables/gov/states/hi/bessd/ccap/hi_ccap_countable_income.py
+++ b/policyengine_us/variables/gov/states/hi/bessd/ccap/hi_ccap_countable_income.py
@@ -8,15 +8,25 @@ class hi_ccap_countable_income(Variable):
     definition_period = MONTH
     unit = USD
     defined_for = StateCode.HI
-    reference = "https://humanservices.hawaii.gov/bessd/files/2013/01/HAR-17-798.2-Child-Care-Services-Rules.pdf#page=19"
+    reference = (
+        # HAR 17-798.3-10 (counted sources) and -11 (exclusions), eff.
+        # 2021-08-06; "gross income" is defined in 17-798.3-2 as all
+        # non-excluded earned and unearned income.
+        "https://humanservices.hawaii.gov/bessd/files/2021/09/CHAPTER-17-798.3-Child-Care-Payments.pdf#page=24",
+        # Superseded HAR 17-798.2-10 and -11, with the same source list,
+        # exclusions, and 17-798.2-2 definition.
+        "https://humanservices.hawaii.gov/bessd/files/2013/01/HAR-17-798.2-Child-Care-Services-Rules.pdf#page=19",
+    )
 
     def formula(spm_unit, period, parameters):
         p = parameters(period).gov.states.hi.bessd.ccap
-        # Monthly gross income from all counted sources (HAR 17-798.2-10(b)).
+        # Monthly gross income from all counted sources (HAR 17-798.3-10(b);
+        # identically 17-798.2-10(b) before August 6, 2021).
         gross = add(spm_unit, period, p.income.countable_income.sources)
-        # HAR 17-798.2-11(8): exclude the earnings of minor household members
-        # who are at least half-time students. is_full_time_student is the
-        # available proxy for a minor's at-least-half-time enrollment.
+        # HAR 17-798.3-11(8) (17-798.2-11(8) before August 6, 2021): exclude
+        # the earnings of minor household members who are at least half-time
+        # students. is_full_time_student is the available proxy for a
+        # minor's at-least-half-time enrollment.
         person = spm_unit.members
         is_minor_student = (
             person("age", period.this_year) < p.age.minor_age_limit