diff --git a/changelog.d/ma-excess-business-loss.fixed.md b/changelog.d/ma-excess-business-loss.fixed.md
new file mode 100644
index 00000000000..7be27950ec5
--- /dev/null
+++ b/changelog.d/ma-excess-business-loss.fixed.md
@@ -0,0 +1 @@
+Add the excess business loss back to Massachusetts 5.0% income for tax years 2022 through 2028 (Schedule X, line 6), measured from 2026 against a Massachusetts threshold that does not adopt the OBBBA reset, with new excess_business_loss and net_business_loss variables.
diff --git a/policyengine_us/parameters/gov/states/ma/tax/income/excess_business_loss/in_effect.yaml b/policyengine_us/parameters/gov/states/ma/tax/income/excess_business_loss/in_effect.yaml
new file mode 100644
index 00000000000..1d391bb5042
--- /dev/null
+++ b/policyengine_us/parameters/gov/states/ma/tax/income/excess_business_loss/in_effect.yaml
@@ -0,0 +1,39 @@
+description: Massachusetts adds the excess business loss back to 5.0% income if this is true.
+
+values:
+  2018-01-01: false
+  # Massachusetts conforms to the Code as amended on January 1, 2022 for tax
+  # years beginning on or after January 1, 2022 (St. 2022, c. 126, ss. 30 and
+  # 189), including Section 461(l) (TIR 23-5), and to the Code as amended on
+  # January 1, 2024 from tax year 2024 (St. 2024, c. 140, ss. 100 and 251).
+  2022-01-01: true
+  # The Code as amended on January 1, 2024 limits excess business losses
+  # through the 2028 taxable year (TIR 24-14). Massachusetts does not conform
+  # to the OBBBA extension of the limitation (TIR 26-4).
+  2029-01-01: false
+
+metadata:
+  unit: bool
+  period: year
+  label: Massachusetts excess business loss add-back in effect
+  reference:
+    - title: M.G.L. c. 62, s. 1(c), definition of Code
+      href: https://malegislature.gov/Laws/GeneralLaws/PartI/TitleIX/Chapter62/Section1
+    - title: TIR 23-1, Tax Provisions in the Fiscal Year 2023 Budget, Including Massachusetts Personal Income Tax Code Update (Code section 461(l))
+      href: https://www.mass.gov/technical-information-release/working-draft-tir-tax-provisions-in-the-fiscal-year-2023-budget-including-massachusetts-personal-income-tax-code-update
+    - title: TIR 23-5, Chapter 62 Conformity to Select Provisions of the 2022 Internal Revenue Code (Code section 461(l))
+      href: https://www.mass.gov/technical-information-release/tir-23-5-chapter-62-conformity-to-select-provisions-of-the-2022-internal-revenue-code
+    - title: TIR 24-14, Tax Provisions in the Fiscal Year 2025 Budget, II.A.1 Limitation on Noncorporate Excess Business Losses
+      href: https://www.mass.gov/technical-information-release/tir-24-14-tax-provisions-in-the-fiscal-year-2025-budget
+    - title: TIR 26-4, Massachusetts Conformity to Certain Provisions in Public Law No. 119-21 (Sec. 70601)
+      href: https://www.mass.gov/technical-information-release/tir-26-4-massachusetts-conformity-to-certain-provisions-in-public-law-no-119-21
+    - title: 2022 Form 1 instructions, Updated IRC Conformity Date ("Code Update")
+      href: https://web.archive.org/web/20230616200742/https://www.mass.gov/doc/2022-form-1-instructions/download#page=4
+    - title: 2022 Form 1 instructions, Schedule X, line 6 Excess Business Loss Adjustment
+      href: https://web.archive.org/web/20230616200742/https://www.mass.gov/doc/2022-form-1-instructions/download#page=20
+    - title: 2023 Form 1 instructions, Schedule X, line 6 Excess Business Loss Adjustment
+      href: https://www.mass.gov/doc/2023-form-1-instructions/download#page=20
+    - title: 2024 Form 1 instructions, Schedule X, line 6 Excess Business Loss Adjustment
+      href: https://www.mass.gov/doc/2024-form-1-instructions/download#page=20
+    - title: 2025 Form 1 instructions, Schedule X, line 6 Excess Business Loss Adjustment
+      href: https://www.mass.gov/doc/2025-form-1-instructions/download#page=21
diff --git a/policyengine_us/parameters/gov/states/ma/tax/income/excess_business_loss/threshold.yaml b/policyengine_us/parameters/gov/states/ma/tax/income/excess_business_loss/threshold.yaml
new file mode 100644
index 00000000000..381fcb62d45
--- /dev/null
+++ b/policyengine_us/parameters/gov/states/ma/tax/income/excess_business_loss/threshold.yaml
@@ -0,0 +1,109 @@
+description: Massachusetts treats business losses above business income plus this threshold as an excess business loss, under Section 461(l) of the Code as Massachusetts adopts it; only joint returns receive twice the nonjoint threshold.
+metadata:
+  propagate_metadata_to_children: true
+  label: Massachusetts excess business loss threshold
+  breakdown:
+    - filing_status
+  unit: currency-USD
+  period: year
+  reference:
+    - title: M.G.L. c. 62, s. 1(c), definition of Code (as amended on January 1, 2024)
+      href: https://malegislature.gov/Laws/GeneralLaws/PartI/TitleIX/Chapter62/Section1
+    - title: TIR 26-4, Massachusetts Conformity to Certain Provisions in Public Law No. 119-21 (Sec. 70601, no conformity)
+      href: https://www.mass.gov/technical-information-release/tir-26-4-massachusetts-conformity-to-certain-provisions-in-public-law-no-119-21
+    - title: Revenue Procedure 2021-45, section 3.32 (2022 threshold)
+      href: https://www.irs.gov/pub/irs-drop/rp-21-45.pdf#page=19
+    - title: Revenue Procedure 2022-38, section 3.32 (2023 threshold)
+      href: https://www.irs.gov/pub/irs-drop/rp-22-38.pdf#page=18
+    - title: Revenue Procedure 2023-34, section 3.32 (2024 threshold)
+      href: https://www.irs.gov/pub/irs-drop/rp-23-34.pdf#page=17
+    - title: Revenue Procedure 2024-40, section 2.32 (2025 threshold)
+      href: https://www.irs.gov/pub/irs-drop/rp-24-40.pdf#page=17
+    - title: 2022 Form 1 instructions, Schedule X, line 6 Excess Business Loss Adjustment
+      href: https://web.archive.org/web/20230616200742/https://www.mass.gov/doc/2022-form-1-instructions/download#page=20
+    - title: 2024 Form 1 instructions, Schedule X, line 6 Excess Business Loss Adjustment
+      href: https://www.mass.gov/doc/2024-form-1-instructions/download#page=20
+    - title: 2025 Form 1 instructions, Schedule X, line 6 Excess Business Loss Adjustment
+      href: https://www.mass.gov/doc/2025-form-1-instructions/download#page=21
+# Through 2025 the Massachusetts threshold is the federal threshold: Schedule X,
+# line 6 is the excess business loss on U.S. Form 1040, Schedule 1, line 8p.
+# The 2023 Form 1 instructions still print $270,000 / $540,000, but line 8p
+# uses the 2023 federal $289,000 / $578,000 (Rev. Proc. 2022-38).
+# From 2026 the federal threshold uses the OBBBA reset ($256,000 / $512,000,
+# Rev. Proc. 2025-32, section 4.31), which Massachusetts does not adopt
+# (TIR 26-4). The 2026 values follow Section 461(l)(3)(C) as of January 1,
+# 2024: $250,000 times the Section 1(f)(3) cost-of-living adjustment with
+# "2017" for "2016" (average C-CPI-U for the 12 months ending August 31),
+# rounded to the nearest $1,000. 250,000 x 177.1137 / 138.2368 = 320,309,
+# so $320,000 ($640,000 joint). The same computation gives every published
+# figure for 2022-2025 (269,580; 289,140; 304,634; 313,038). The Department
+# of Revenue has not printed a 2026 figure (TIR 26-4; 2025 Form 1
+# instructions, page 21). 320,309 is about $200 below the 320,500 rounding
+# boundary, so a different CPI series could give $321,000.
+HEAD_OF_HOUSEHOLD:
+  metadata:
+    uprating:
+      parameter: gov.irs.uprating
+      rounding:
+        type: nearest
+        interval: 1_000
+  values:
+    2022-01-01: 270_000
+    2023-01-01: 289_000
+    2024-01-01: 305_000
+    2025-01-01: 313_000
+    2026-01-01: 320_000
+JOINT:
+  metadata:
+    uprating:
+      parameter: gov.irs.uprating
+      rounding:
+        # Twice the rounded nonjoint threshold under section 461(l)(3).
+        type: nearest
+        interval: 2_000
+  values:
+    2022-01-01: 540_000
+    2023-01-01: 578_000
+    2024-01-01: 610_000
+    2025-01-01: 626_000
+    2026-01-01: 640_000
+SEPARATE:
+  metadata:
+    uprating:
+      parameter: gov.irs.uprating
+      rounding:
+        type: nearest
+        interval: 1_000
+  values:
+    2022-01-01: 270_000
+    2023-01-01: 289_000
+    2024-01-01: 305_000
+    2025-01-01: 313_000
+    2026-01-01: 320_000
+SINGLE:
+  metadata:
+    uprating:
+      parameter: gov.irs.uprating
+      rounding:
+        type: nearest
+        interval: 1_000
+  values:
+    2022-01-01: 270_000
+    2023-01-01: 289_000
+    2024-01-01: 305_000
+    2025-01-01: 313_000
+    2026-01-01: 320_000
+SURVIVING_SPOUSE:
+  metadata:
+    uprating:
+      parameter: gov.irs.uprating
+      rounding:
+        type: nearest
+        interval: 1_000
+  # Section 461(l)(3)(A) doubles the threshold only for a joint return.
+  values:
+    2022-01-01: 270_000
+    2023-01-01: 289_000
+    2024-01-01: 305_000
+    2025-01-01: 313_000
+    2026-01-01: 320_000
diff --git a/policyengine_us/tests/policy/baseline/gov/irs/income/taxable_income/adjusted_gross_income/above_the_line_deductions/excess_business_loss.yaml b/policyengine_us/tests/policy/baseline/gov/irs/income/taxable_income/adjusted_gross_income/above_the_line_deductions/excess_business_loss.yaml
new file mode 100644
index 00000000000..198e0945d8f
--- /dev/null
+++ b/policyengine_us/tests/policy/baseline/gov/irs/income/taxable_income/adjusted_gross_income/above_the_line_deductions/excess_business_loss.yaml
@@ -0,0 +1,82 @@
+- name: An S corporation loss above the 2022 joint threshold is an excess business loss
+  period: 2022
+  input:
+    people:
+      head:
+        age: 50
+        partnership_s_corp_income: -1_000_000
+      spouse:
+        age: 50
+    tax_units:
+      tax_unit:
+        members: [head, spouse]
+    households:
+      household:
+        members: [head, spouse]
+        state_code: TX
+  output:
+    net_business_loss: 1_000_000
+    # 1,000,000 - 540,000 (Rev. Proc. 2021-45)
+    excess_business_loss: 460_000
+    loss_ald: 540_000
+
+- name: Business income of the other spouse raises the allowed loss
+  period: 2022
+  input:
+    people:
+      head:
+        age: 50
+        partnership_s_corp_income: -1_000_000
+      spouse:
+        age: 50
+        self_employment_income: 200_000
+    tax_units:
+      tax_unit:
+        members: [head, spouse]
+    households:
+      household:
+        members: [head, spouse]
+        state_code: TX
+  output:
+    # 1,000,000 - (200,000 + 540,000)
+    excess_business_loss: 260_000
+
+- name: No excess business loss below the 2025 single threshold
+  period: 2025
+  input:
+    people:
+      head:
+        age: 50
+        self_employment_income: -300_000
+    tax_units:
+      tax_unit:
+        members: [head]
+    households:
+      household:
+        members: [head]
+        state_code: TX
+  output:
+    # The 2025 single threshold is $313,000 (Form 461, line 15).
+    excess_business_loss: 0
+
+- name: A dependent's business loss is on their own return
+  period: 2022
+  input:
+    people:
+      head:
+        age: 50
+        partnership_s_corp_income: -400_000
+      dependent:
+        age: 20
+        is_tax_unit_dependent: true
+        partnership_s_corp_income: -500_000
+    tax_units:
+      tax_unit:
+        members: [head, dependent]
+    households:
+      household:
+        members: [head, dependent]
+        state_code: TX
+  output:
+    # 400,000 - 270,000
+    excess_business_loss: 130_000
diff --git a/policyengine_us/tests/policy/baseline/gov/states/ma/tax/income/gross_income/ma_excess_business_loss_adjustment.yaml b/policyengine_us/tests/policy/baseline/gov/states/ma/tax/income/gross_income/ma_excess_business_loss_adjustment.yaml
new file mode 100644
index 00000000000..26fa9401fa3
--- /dev/null
+++ b/policyengine_us/tests/policy/baseline/gov/states/ma/tax/income/gross_income/ma_excess_business_loss_adjustment.yaml
@@ -0,0 +1,210 @@
+# Massachusetts adds the federal excess business loss (Schedule 1, line 8p)
+# back to 5.0% income from 2022 (Schedule X, line 6). From 2026 the loss is
+# measured against the Massachusetts threshold, not the OBBBA-reset federal
+# one, and the add-back ends after 2028. The interest is Massachusetts bank
+# interest, so it is 5.0% income.
+
+- name: 2022 joint return adds back the loss above $540,000
+  period: 2022
+  absolute_error_margin: 0.01
+  input:
+    people:
+      head:
+        age: 50
+        taxable_interest_income: 2_000_000
+        partnership_s_corp_income: -1_000_000
+      spouse:
+        age: 50
+    tax_units:
+      tax_unit:
+        members: [head, spouse]
+    households:
+      household:
+        members: [head, spouse]
+        state_code: MA
+  output:
+    ma_excess_business_loss_adjustment: 460_000
+    # 2,000,000 - 1,000,000 + 460,000
+    ma_gross_income: 1_460_000
+    # 1,460,000 - 200 bank interest exemption - 8,800 exemption
+    ma_part_b_taxable_income: 1_451_000
+    ma_income_tax_before_credits: 72_550
+
+- name: 2022 single return adds back the loss above $270,000
+  period: 2022
+  absolute_error_margin: 0.01
+  input:
+    people:
+      head:
+        age: 50
+        taxable_interest_income: 2_000_000
+        partnership_s_corp_income: -1_000_000
+    tax_units:
+      tax_unit:
+        members: [head]
+    households:
+      household:
+        members: [head]
+        state_code: MA
+  output:
+    ma_excess_business_loss_adjustment: 730_000
+    # 2,000,000 - 270,000 - 100 bank interest exemption - 4,400 exemption
+    ma_part_b_taxable_income: 1_725_500
+
+- name: 2024 joint return uses the $610,000 threshold
+  period: 2024
+  absolute_error_margin: 0.01
+  input:
+    people:
+      head:
+        age: 50
+        taxable_interest_income: 2_000_000
+        partnership_s_corp_income: -1_000_000
+      spouse:
+        age: 50
+    tax_units:
+      tax_unit:
+        members: [head, spouse]
+    households:
+      household:
+        members: [head, spouse]
+        state_code: MA
+  output:
+    ma_excess_business_loss_adjustment: 390_000
+    # 2,000,000 - 610,000 - 8,800 exemption (no bank interest exemption from 2024)
+    ma_part_b_taxable_income: 1_381_200
+
+- name: No add-back in 2021, before the Code Update
+  period: 2021
+  absolute_error_margin: 0.01
+  input:
+    people:
+      head:
+        age: 50
+        taxable_interest_income: 2_000_000
+        partnership_s_corp_income: -1_000_000
+      spouse:
+        age: 50
+    tax_units:
+      tax_unit:
+        members: [head, spouse]
+    households:
+      household:
+        members: [head, spouse]
+        state_code: MA
+  output:
+    ma_excess_business_loss_adjustment: 0
+    # 2,000,000 - 1,000,000 - 200 - 8,800
+    ma_part_b_taxable_income: 991_000
+
+- name: 2023 single return with a loss equal to the $289,000 threshold adds back nothing
+  period: 2023
+  absolute_error_margin: 0.01
+  input:
+    people:
+      head:
+        age: 50
+        self_employment_income: -289_000
+    tax_units:
+      tax_unit:
+        members: [head]
+    households:
+      household:
+        members: [head]
+        state_code: MA
+  output:
+    # 289,000 - 289,000 (Rev. Proc. 2022-38, section 3.32) = 0. Schedule X,
+    # line 6 is the line 8p amount, although the 2023 instructions print
+    # $270,000, which would give 19,000.
+    excess_business_loss: 0
+    ma_excess_business_loss_adjustment: 0
+
+- name: 2026 single return with a loss equal to the $320,000 Massachusetts threshold adds back nothing
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      head:
+        age: 50
+        self_employment_income: -320_000
+    tax_units:
+      tax_unit:
+        members: [head]
+    households:
+      household:
+        members: [head]
+        state_code: MA
+  output:
+    # Federal: 320,000 - 256,000 (Rev. Proc. 2025-32, section 4.31)
+    excess_business_loss: 64_000
+    # Massachusetts: 320,000 - 320,000 = 0 (no OBBBA reset, TIR 26-4)
+    ma_excess_business_loss_adjustment: 0
+
+- name: 2026 single return with wages and a Schedule C loss below the Massachusetts threshold
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      head:
+        age: 50
+        employment_income: 500_000
+        self_employment_income: -300_000
+    tax_units:
+      tax_unit:
+        members: [head]
+    households:
+      household:
+        members: [head]
+        state_code: MA
+  output:
+    # Federal: 300,000 - 256,000
+    excess_business_loss: 44_000
+    # Massachusetts: 300,000 is below 320,000.
+    ma_excess_business_loss_adjustment: 0
+    # 500,000 wages - 300,000 Form 1, line 6a loss + 0
+    ma_gross_income: 200_000
+
+- name: 2026 joint return adds back the loss above $640,000
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      head:
+        age: 50
+        partnership_s_corp_income: -1_000_000
+      spouse:
+        age: 50
+    tax_units:
+      tax_unit:
+        members: [head, spouse]
+    households:
+      household:
+        members: [head, spouse]
+        state_code: MA
+  output:
+    # Federal: 1,000,000 - 512,000
+    excess_business_loss: 488_000
+    # Massachusetts: 1,000,000 - 640,000
+    ma_excess_business_loss_adjustment: 360_000
+
+- name: No add-back from 2029, after the limitation ends
+  period: 2029
+  absolute_error_margin: 0.01
+  input:
+    people:
+      head:
+        age: 50
+        partnership_s_corp_income: -1_000_000
+      spouse:
+        age: 50
+    tax_units:
+      tax_unit:
+        members: [head, spouse]
+    households:
+      household:
+        members: [head, spouse]
+        state_code: MA
+  output:
+    # The Code as amended on January 1, 2024 limits excess business losses
+    # through the 2028 taxable year (TIR 24-14).
+    ma_excess_business_loss_adjustment: 0
diff --git a/policyengine_us/variables/gov/irs/income/taxable_income/adjusted_gross_income/above_the_line_deductions/excess_business_loss.py b/policyengine_us/variables/gov/irs/income/taxable_income/adjusted_gross_income/above_the_line_deductions/excess_business_loss.py
new file mode 100644
index 00000000000..2ffe5180fe1
--- /dev/null
+++ b/policyengine_us/variables/gov/irs/income/taxable_income/adjusted_gross_income/above_the_line_deductions/excess_business_loss.py
@@ -0,0 +1,24 @@
+from policyengine_us.model_api import *
+
+
+class excess_business_loss(Variable):
+    value_type = float
+    entity = TaxUnit
+    label = "Excess business loss"
+    unit = USD
+    documentation = (
+        "Business losses above business income plus the Section 461(l) "
+        "threshold, which loss_ald does not deduct (Form 461, line 16; "
+        "Form 1040, Schedule 1, line 8p)."
+    )
+    definition_period = YEAR
+    reference = (
+        "https://www.law.cornell.edu/uscode/text/26/461#l",
+        "https://www.irs.gov/pub/irs-prior/f461--2025.pdf",
+    )
+
+    def formula(tax_unit, period, parameters):
+        filing_status = tax_unit("filing_status", period)
+        threshold = parameters(period).gov.irs.ald.loss.max[filing_status]
+        net_business_loss = tax_unit("net_business_loss", period)
+        return max_(0, net_business_loss - threshold)
diff --git a/policyengine_us/variables/gov/irs/income/taxable_income/adjusted_gross_income/above_the_line_deductions/net_business_loss.py b/policyengine_us/variables/gov/irs/income/taxable_income/adjusted_gross_income/above_the_line_deductions/net_business_loss.py
new file mode 100644
index 00000000000..43268f9c73e
--- /dev/null
+++ b/policyengine_us/variables/gov/irs/income/taxable_income/adjusted_gross_income/above_the_line_deductions/net_business_loss.py
@@ -0,0 +1,37 @@
+from policyengine_us.model_api import *
+
+
+class net_business_loss(Variable):
+    value_type = float
+    entity = TaxUnit
+    label = "Net business loss"
+    unit = USD
+    documentation = (
+        "Aggregate business deductions above aggregate business income and "
+        "gains, before the Section 461(l) threshold (Form 461, line 14, as a "
+        "positive amount)."
+    )
+    definition_period = YEAR
+    reference = (
+        "https://www.law.cornell.edu/uscode/text/26/461#l_3_A",
+        "https://www.irs.gov/pub/irs-prior/f461--2025.pdf",
+    )
+
+    def formula(tax_unit, period, parameters):
+        # The same head and spouse business items as loss_ald. The excess of
+        # aggregate business deductions over aggregate business income is
+        # the negative of their net total.
+        net_business_income = tax_unit_non_dep_add(
+            tax_unit,
+            period,
+            [
+                "total_self_employment_income",
+                "farm_operations_income",
+                "rental_income",
+                "farm_rent_income",
+                "estate_income",
+                "partnership_s_corp_income",
+                "other_net_gain",
+            ],
+        )
+        return max_(0, -net_business_income)
diff --git a/policyengine_us/variables/gov/states/ma/tax/income/gross_income/ma_excess_business_loss_adjustment.py b/policyengine_us/variables/gov/states/ma/tax/income/gross_income/ma_excess_business_loss_adjustment.py
new file mode 100644
index 00000000000..1cf161eb6db
--- /dev/null
+++ b/policyengine_us/variables/gov/states/ma/tax/income/gross_income/ma_excess_business_loss_adjustment.py
@@ -0,0 +1,30 @@
+from policyengine_us.model_api import *
+
+
+class ma_excess_business_loss_adjustment(Variable):
+    value_type = float
+    entity = TaxUnit
+    label = "MA excess business loss adjustment"
+    documentation = (
+        "Massachusetts Schedule X, line 6: the excess business loss under "
+        "Section 461(l) as Massachusetts adopts it, added back to 5.0% income."
+    )
+    unit = USD
+    definition_period = YEAR
+    reference = (
+        "https://www.mass.gov/doc/2024-form-1-instructions/download#page=20",
+        "https://www.mass.gov/doc/2025-form-1-instructions/download#page=21",
+        "https://www.mass.gov/technical-information-release/tir-26-4-massachusetts-conformity-to-certain-provisions-in-public-law-no-119-21",
+    )
+    defined_for = StateCode.MA
+
+    def formula(tax_unit, period, parameters):
+        p = parameters(period).gov.states.ma.tax.income.excess_business_loss
+        filing_status = tax_unit("filing_status", period)
+        # Through 2025 this is the federal excess business loss (Form 1040,
+        # Schedule 1, line 8p). Massachusetts does not adopt the OBBBA
+        # threshold reset from 2026, so the loss is measured against the
+        # Massachusetts threshold.
+        net_business_loss = tax_unit("net_business_loss", period)
+        excess_business_loss = max_(0, net_business_loss - p.threshold[filing_status])
+        return p.in_effect * excess_business_loss
diff --git a/policyengine_us/variables/gov/states/ma/tax/income/gross_income/ma_gross_income.py b/policyengine_us/variables/gov/states/ma/tax/income/gross_income/ma_gross_income.py
index 02d305f5263..ca107287104 100644
--- a/policyengine_us/variables/gov/states/ma/tax/income/gross_income/ma_gross_income.py
+++ b/policyengine_us/variables/gov/states/ma/tax/income/gross_income/ma_gross_income.py
@@ -20,6 +20,8 @@ def formula(tax_unit, period, parameters):
         federal_gross_income = add(tax_unit, period, ["irs_gross_income"])
         # Add back lines 6/7 losses dropped by irs_gross_income.
         loss_adjustment = tax_unit("ma_gross_income_loss_adjustment", period)
+        # Add back the excess business loss (Schedule X, line 6).
+        excess_business_loss = tax_unit("ma_excess_business_loss_adjustment", period)
         # Under M.G.L. c. 62 § 2(a)(1)(C), earned income from foreign sources
         # excluded under section 911 of the Code is added to MA gross income.
         # It is neither interest, dividends nor capital gains, so the Part B
@@ -47,5 +49,9 @@ def formula(tax_unit, period, parameters):
         deductions = social_security_in_agi + salt_refund_income + public_pension
         return max_(
             0,
-            federal_gross_income + loss_adjustment + foreign_earned_income - deductions,
+            federal_gross_income
+            + loss_adjustment
+            + excess_business_loss
+            + foreign_earned_income
+            - deductions,
         )