A score is built in three steps, the way CBO and JCT build theirs. This page sets out each step, the numbers it rests on, and how far the results sit from published scores.
The direct change in revenue, holding behaviour fixed. For a rate change: the change in rate, times the income above the threshold, times the number of filers it reaches. Only income above the threshold counts.
People respond to a tax change by earning, reporting or timing income differently. For income tax the offset is half the static effect times the elasticity of taxable income (0.25), which shrinks a rise and a cut alike. Capital gains, corporate, trade and the other modules each carry their own response.
The “with economic feedback” view runs the change through multipliers calibrated to the Federal Reserve's FRB/US model, books the revenue that follows from higher or lower output, and nets the interest on the extra debt. It has no long-run supply channel.
| Parameter | Value | Source |
|---|---|---|
| Elasticity of taxable income | 0.25 | Saez, Slemrod and Giertz (2012) |
| Capital gains response to the tax rate | 0.72 lasting, 1.20 in the first year, at a 22% reference rate | Dowd, McClelland and Muthitacharoen (2015); CRS R48562 |
| Spending multiplier, year 1 | 1.4, fading 25% a year | FRB/US calibration |
| Tax multiplier, year 1 | 0.7 | FRB/US calibration |
| Demand effect kept each year | 65% | FRB/US calibration (monetary offset) |
| Crowding out | 15% of the cumulative deficit | Literature estimate |
| Revenue from extra output | 25 cents per dollar | CBO |
| Labour and capital shares | 0.65 and 0.35 | BLS |
| Tariff income and payroll offset | 0.244 in 2025 falling to 0.241 in 2035 | JCT, via CBO's tariff model |
| Corporate base | CBO's corporate receipts path, scaled to the tax base | CBO publication 59710; IRS SOI |
There are two kinds of check, and they answer different questions, so they are never pooled into one accuracy figure.
The honest test. Across 44 published scores, mostly from CBO's Options for Reducing the Deficit, the calculator is off by 15.2% on average (12.3% for the middle case). 26 of 44 land within 15% and 36 of 44 within 25%. The error depends a great deal on the kind of policy:
| Kind of policy | Cases | Average gap | Within 15% |
|---|---|---|---|
| Discretionary spending | 5 | 4.6% | 5 |
| Tax expenditure | 2 | 7.1% | 2 |
| AGI-inclusive surtax | 4 | 7.2% | 3 |
| Enacted-law spending | 3 | 7.4% | 3 |
| Capital gains | 7 | 14.4% | 4 |
| Ordinary rate change | 11 | 15.3% | 6 |
| Payroll | 8 | 18.6% | 4 |
| Corporate | 4 | 40.3% | 0 |
For 15 policies a module constant was fitted so the model reproduces the published score. Their average gap of 1.6% is low by construction. Holding in place the rows whose published target was later corrected, the same group reads 12.4% over 26.
Another 38 policies are scored against a published figure nothing is fitted to. Their average gap is 42.3% (30.1% for the middle case).
With the 2 withdrawn targets held in place at the error they carried, it is 60% over 40.
A third check refits each fitted module without one of its targets and asks whether it can put that target back. Across 18 such cases the gap is 36.3% on average (4 more cannot be tested this way).
Built bottom-up from IRS filer counts, the CBO baseline and each module's revenue arithmetic. Nothing was tuned to these targets, and each was registered before it was first scored.
| Policy | Published | Calculator | Gap |
|---|---|---|---|
| CBO Option 37: Cut International Affairs Funding 25%Congressional Budget Office, 2024-12 | -$187.0B | -$186.9B | 0.0% |
| CBO 2022 Option 13: 1pp AGI Surtax Above the Standard DeductionJoint Committee on Taxation, 2022-12 | -$1,329.1B | -$1,325.7B | 0.3% |
| IIJA 2021: discretionary spending component (outlays)Congressional Budget Office, 2021-08 | +$415.4B | +$414.3B | 0.3% |
| CBO 2018 Option 1: Top Two Brackets +1ppJoint Committee on Taxation, 2018-12 | -$123.4B | -$124.4B | 0.8% |
| CBO 2018 Option 1: All Ordinary Rates +1ppJoint Committee on Taxation, 2018-12 | -$905.4B | -$912.7B | 0.8% |
| CBO 2022 Option 6: Limit the Income-Tax Exclusion for Employer Health BenefitsCongressional Budget Office, 2022-12 | -$651.4B | -$659.9B | 1.3% |
| CBO Option 45: All Ordinary Rates +1ppCongressional Budget Office, 2024-12 | -$1,185.3B | -$1,201.2B | 1.3% |
| CBO Option 42: Cut Selected Nondefense Discretionary SpendingCongressional Budget Office, 2024-12 | -$339.0B | -$333.3B | 1.7% |
| Treasury: 39.6% + Eliminate Step-UpU.S. Treasury, 2021-05 | -$322.0B | -$316.1B | 1.8% |
| CBO 2020 Option 2: LTCG and Qualified Dividends +2ppJoint Committee on Taxation, 2020-12 | -$75.2B | -$73.8B | 1.9% |
| CBO Option 46: 2pp AGI Surtax Above $100KCongressional Budget Office, 2024-12 | -$1,051.0B | -$1,075.8B | 2.4% |
| CBO Option 38: End National Community Service FundingCongressional Budget Office, 2024-12 | -$10.3B | -$10.6B | 2.6% |
| CBO 2018 Option 2: LTCG and Qualified Dividends +2ppJoint Committee on Taxation, 2018-12 | -$69.6B | -$65.9B | 5.3% |
| CBO Option 61: New 1% Payroll Tax on All EarningsCongressional Budget Office, 2024-12 | -$1,281.5B | -$1,378.2B | 7.5% |
| CBO Option 46: 1pp AGI Surtax Above $20KCongressional Budget Office, 2024-12 | -$1,440.1B | -$1,326.3B | 7.9% |
| CBO Option 39: Tighten Pell Grant EligibilityCongressional Budget Office, 2024-12 | -$22.1B | -$20.3B | 8.1% |
| CBO Option 61: New 2% Payroll Tax on All EarningsCongressional Budget Office, 2024-12 | -$2,540.0B | -$2,745.0B | 8.1% |
| Social Security Fairness Act: WEP/GPO repeal (direct spending)Congressional Budget Office, 2024-09 | +$195.7B | +$214.8B | 9.8% |
| CBO Option 47: LTCG and Qualified Dividends +2ppCongressional Budget Office, 2024-12 | -$103.3B | -$92.5B | 10.5% |
| CBO Option 43: Cut Certain State and Local GrantsCongressional Budget Office, 2024-12 | -$66.7B | -$73.9B | 10.8% |
| CBO 2022 Option 15: New 1% Payroll Tax on EarningsJoint Committee on Taxation, 2022-12 | -$1,135.7B | -$1,273.2B | 12.1% |
| Fiscal Responsibility Act 2023: discretionary caps (outlays)Congressional Budget Office, 2023-05 | -$1,331.8B | -$1,169.5B | 12.2% |
| CBO 2018 Option 1: Top Four Brackets +1ppJoint Committee on Taxation, 2018-12 | -$222.9B | -$250.7B | 12.5% |
| CBO 2022 Option 15: New 2% Payroll Tax on EarningsJoint Committee on Taxation, 2022-12 | -$2,252.7B | -$2,536.0B | 12.6% |
| CBO Option 56: Limit the Income-Tax Exclusion for Employer Health BenefitsCongressional Budget Office, 2024-12 | -$697.0B | -$608.1B | 12.8% |
| 1pp Rate Increase (All Brackets)Joint Committee on Taxation, 2022-12 | -$1,081.3B | -$1,235.7B | 14.3% |
| CBO 2020 Option 1: All Ordinary Rates +1ppJoint Committee on Taxation, 2020-12 | -$884.0B | -$1,016.7B | 15.0% |
| CBO Option 45: Top Four Brackets +2ppCongressional Budget Office, 2024-12 | -$569.5B | -$671.2B | 17.9% |
| CBO 2022 Option 13: 2pp AGI Surtax Above the Fourth BracketJoint Committee on Taxation, 2022-12 | -$773.8B | -$914.3B | 18.2% |
| CBO 2022 Option 37: LTCG and Qualified Dividends +2ppJoint Committee on Taxation, 2022-12 | -$102.1B | -$82.6B | 19.1% |
| CBO 2020 Option 1: Top Two Brackets +1ppJoint Committee on Taxation, 2020-12 | -$113.8B | -$136.5B | 19.9% |
| CBO 2018 Option 18: Medicare HI Payroll Rate +1ppJoint Committee on Taxation, 2018-12 | -$898.3B | -$1,079.0B | 20.1% |
| CBO 2018 Option 18: Medicare HI Payroll Rate +2ppJoint Committee on Taxation, 2018-12 | -$1,786.5B | -$2,149.2B | 20.3% |
| CBO 2020 Option 19: Corporate Rate +1ppJoint Committee on Taxation, 2020-12 | -$99.3B | -$120.9B | 21.8% |
| Biden High-Income Tax IncreaseU.S. Treasury, 2024-03 | -$245.9B | -$299.8B | 21.9% |
| CBO 2022 Option 13: Top Four Brackets +2ppJoint Committee on Taxation, 2022-12 | -$501.9B | -$621.4B | 23.8% |
| Biden Capital Gains at Ordinary Rates (FY2025 Green Book)U.S. Treasury, 2024-03 | -$288.6B | -$366.4B | 27.0% |
| CBO 2020 Option 15: Medicare HI Payroll Rate +1ppJoint Committee on Taxation, 2020-12 | -$877.5B | -$1,173.3B | 33.7% |
| CBO 2020 Option 15: Medicare HI Payroll Rate +2ppJoint Committee on Taxation, 2020-12 | -$1,736.3B | -$2,336.9B | 34.6% |
| CBO Option 51: Tax Accrued Gains at DeathCongressional Budget Office, 2024-12 | -$536.1B | -$345.9B | 35.5% |
| CBO 2020 Option 1: Top Four Brackets +1ppJoint Committee on Taxation, 2020-12 | -$203.3B | -$285.9B | 40.6% |
| CBO 2022 Option 50: Corporate Rate +1ppJoint Committee on Taxation, 2022-12 | -$129.3B | -$183.1B | 41.6% |
| CBO Option 64: Corporate Rate +1ppJoint Committee on Taxation, 2024-12 | -$135.7B | -$196.1B | 44.5% |
| CBO 2018 Option 24: Corporate Rate +1ppJoint Committee on Taxation, 2018-12 | -$96.3B | -$147.8B | 53.4% |
A constant in the module was chosen so the model reproduces this score. Small errors here are by construction and say little about accuracy.
| Policy | Published | Calculator | Gap |
|---|---|---|---|
| Biden 2021 ARP-style CTC (permanent)CBO/JCT 2021, 2021-12 | +$1,600.0B | +$1,600.0B | 0.0% |
| Extend current CTC beyond 2025CBO 2024, 2024-11 | +$600.0B | +$600.0B | 0.0% |
| Estate reform ($3.5M exemption, 45% rate)JCT letter on the 'For the 99.5 Percent Act' (24 March 2021), 2021-03 | -$450.0B | -$450.0B | 0.0% |
| SS cap to cover 90% of wagesCBO, 2018-12 | -$800.0B | -$800.0B | 0.0% |
| Eliminate SS wage capSocial Security Trustees, 2025 | -$3,200.0B | -$3,200.0B | 0.0% |
| Expand NIIT to pass-through incomeJCT (Build Back Better), 2021-11 | -$250.0B | -$250.0B | 0.0% |
| Extend TCJA estate exemption (~$14M)CBO, 2024-11 | +$167.0B | +$167.0B | 0.0% |
| Repeal corporate AMT (CAMT)CBO, 2022-08 | +$220.0B | +$220.1B | 0.0% |
| Cap employer health exclusion at $50KCBO, 2024 | -$450.0B | -$449.5B | 0.1% |
| Repeal individual AMT (post-2025)CBO baseline, 2024 | +$450.0B | +$450.5B | 0.1% |
| Full TCJA extension (all provisions)Congressional Budget Office, 2024-05 | +$4,600.0B | +$4,581.9B | 0.4% |
| Carbon tax at $50/ton with a 5% escalatorCBO-style estimate (no published score), 2024 | -$1,700.0B | -$1,714.8B | 0.9% |
| Biden Corporate Rate to 28%U.S. Treasury, 2024-03 | -$1,347.0B | -$1,292.6B | 4.0% |
| Eliminate step-up in basisBiden proposal, 2021-05 | -$500.0B | -$523.5B | 4.7% |
| TCJA extension without SALT capCBO | +$5,700.0B | +$6,494.5B | 13.9% |
Scored against a published figure no constant is fitted to. A miss here is a finding about the model.
| Policy | Published | Calculator | Gap |
|---|---|---|---|
| Repeal SALT $10K capPenn Wharton Budget Model, Table 3 (Feb 2024), 2024-02 | +$1,169.0B | +$1,155.6B | 1.1% |
| IRA IRS enforcement funding ($80B/10yr)Congressional Budget Office, publication 58390 (August 2022), 2022-08 | -$180.4B | -$188.9B | 4.7% |
| P.L. 119-21: Extension and enhancement of increased child tax creditJoint Committee on Taxation, 2025-07 | +$816.8B | +$863.3B | 5.7% |
| P.L. 119-21: Extension and enhancement of increased estate and gift tax exemption amountsJoint Committee on Taxation, 2025-07 | +$211.7B | +$195.2B | 7.8% |
| Repeal IRA clean-energy tax creditsCBO, budgetary effects of the energy-related tax provisions of P.L. 117-169 (upward revision), 2025-05 | -$851.0B | -$783.0B | 8.0% |
| Extend enhanced PTCs (ARPA/IRA)CBO/JCT pub. 60437 (June 2024), 2024-06 | +$335.0B | +$366.2B | 9.3% |
| Biden childless EITC expansionTreasury FY2025 Green Book (report p. 242), 2024-03 | +$162.6B | +$178.0B | 9.5% |
| Reciprocal tariffs (~20pp average increase)CRFB, 'How Much Will Trump's New Tariffs Raise?' (a published range across three modellers), 2025-04 | -$1,800.0B to -$1,400.0B | -$1,654.7B | 10.3% |
| Cap charitable deduction at 28%Obama/Biden proposal, 2016-02 | -$200.0B | -$174.9B | 12.5% |
| CBO +2pp rate increase across all bracketsJoint Committee on Taxation, 2018-12 | -$70.0B | -$79.8B | 14.0% |
| Eliminate estate taxTax Foundation, Options 3.0, Option 83, 2026-07 | +$407.2B | +$350.0B | 14.0% |
| Eliminate SALT deduction entirelyCBO pub. 60557, Option 49 (report p. 59), 2024-12 | -$1,621.0B | -$1,260.3B | 22.3% |
| Adopt OECD Pillar Two (15% global minimum)Joint Committee on Taxation, 2023-06 | -$102.6B to +$56.5B | -$61.2B | 23.5% |
| Repeal premium tax creditsCBO estimate, 2024 | -$1,100.0B | -$840.8B | 23.6% |
| P.L. 119-21: Extension and enhancement of increased standard deductionJoint Committee on Taxation, 2025-07 | +$1,424.7B | +$1,078.9B | 24.3% |
| Repeal the EV purchase tax creditsJoint Committee on Taxation (JCX-35-25), 2025-07 | -$182.3B | -$228.4B | 25.3% |
| P.L. 119-21: Extension and limited enhancement of reduced ratesJoint Committee on Taxation, 2025-07 | +$2,193.4B | +$2,752.8B | 25.5% |
| PWBM 39.6% rate (with step-up basis at death)Penn Wharton Budget Model, 2021-04 | +$33.0B | +$23.6B | 28.4% |
| Repeal the FDII deductionU.S. Treasury, General Explanations of the Administration's FY2025 Revenue Proposals (Green Book), 2024-03 | -$158.0B | -$110.7B | 29.9% |
| Eliminate mortgage interest deductionTax Foundation, Options 3.0, Option 25 (range anchor), 2026-07 | -$495.0B to -$367.9B | -$256.8B | 30.2% |
| Trump universal 10% tariffTax Foundation (Fiscal Fact 861), 2025-04 | -$2,171.1B | -$1,380.4B | 36.4% |
| Biden GILTI reform (country-by-country, 21%)U.S. Treasury, General Explanations of the Administration's FY2025 Revenue Proposals (Green Book), 2024-03 | -$373.9B | -$230.3B | 38.4% |
| Universal $35/month insulin capCongressional Budget Office, 2022-03 | +$11.4B | +$7.0B | 39.0% |
| Biden international package (GILTI + FDII + UTPR)U.S. Treasury, General Explanations of the Administration's FY2025 Revenue Proposals (Green Book), 2024-03 | -$632.2B | -$353.7B | 44.1% |
| Extend rate cuts only (no other provisions)CBO, 2024-11 | +$2,158.7B | +$3,114.7B | 44.3% |
| P.L. 119-21: Termination of deduction for personal exemptions other than temporary senior deductionJoint Committee on Taxation, 2025-07 | -$1,807.1B | -$989.0B | 45.3% |
| P.L. 119-21: Extension of increased alternative minimum tax exemption amounts, modification of phaseout thresholds, and increased threshold phaseout rateJoint Committee on Taxation, 2025-07 | +$1,362.8B | +$719.3B | 47.2% |
| Trump 60% China tariffTax Foundation, 2024-12 | -$650.0B | -$333.7B | 48.7% |
| 25% tariff on imported autos and partsTax Foundation (Trump Tariffs tracker, Table 5), 2026-08 | -$386.2B | -$576.3B | 49.2% |
| Biden Corporate Rate to 28% (FY2022 Green Book)U.S. Treasury, Office of Tax Analysis, 2021-05 | -$857.8B | -$1,292.6B | 50.7% |
| P.L. 119-21: Extension and enhancement of deduction for qualified business incomeJoint Committee on Taxation, 2025-07 | +$736.5B | +$1,123.9B | 52.6% |
| Extend TCJA AMT reliefCRS R48286 Table 1 (transcribing CBO 60114/60271), 2024-11 | +$1,357.1B | +$450.5B | 66.8% |
| PWBM 39.6% rate (without step-up basis)Penn Wharton Budget Model, 2021-04 | -$113.0B | -$26.6B | 76.5% |
| P.L. 119-21: Limitation on individual deductions for certain State and local taxesJoint Committee on Taxation, 2025-07 | -$946.2B | -$1,685.8B | 78.2% |
| Double IRS enforcement beyond IRA levelsU.S. Treasury, 'The Case for a Robust Attack on the Tax Gap' (2021); Sarin & Summers enforcement estimates, 2021-05 | -$340.0B | -$60.3B | 82.3% |
| SS tax on wages above $250KCBO, Options 2025-2034, Option 62 alternative 2, 2024-12 | -$1,426.8B | -$2,700.0B | 89.2% |
| Trump Corporate Rate to 15%Tax Foundation / Penn Wharton Budget Model, 2024-07 | +$595.0B to +$673.1B | +$1,545.2B | 129.6% |
| 25% tariff on steel and aluminiumTax Foundation, 2024 | -$60.0B | -$214.9B | 258.1% |
The target turned out not to be a published score of this policy. The row stays on the record with the error it carried when withdrawn.
| Policy | Published | Calculator | Gap |
|---|---|---|---|
| Expand Medicare drug negotiation to 50 drugsCBO (IRA baseline) extended by model estimate, 2023 | -$500.0B | -$33.5B | 93.3% |
| International reference pricing for Medicare drugsRAND price-comparison study, extended by model estimate, 2021 | -$100.0B | -$801.0B | 701.0% |
The full methods, every figure the model is checked against and its source, and the code are in the repository. See also About.