Principles
- Annual liability, not payroll withholding. KeptOffer shows what you owe for the tax year. Your payslips can differ month to month; the difference is settled when you file or at year end.
- Every rate and threshold is a rule with a source. Rules come from tax authorities and official publications (GOV.UK and HMRC, the ATO, the CRA, the IRS, the SSA, California's FTB and EDD, New York's Department of Taxation and Finance), and a text snapshot of each source is kept with the code.
- Each rule has a status. Confirmed means read from the official source for that year. Assumption means a modelling choice or a value held from the previous year because the new one is not published yet; it is shown next to any result it affects.
- Every number in the text of the site is calculated by the same engine when the page is built. Nothing is typed in by hand.
- Tests reproduce official worked examples to the cent: ATO examples for HELP, Medicare and the surcharge; GOV.UK examples for student loans and relief-at-source pensions; CRA contribution maximums; and every constant on New York's 2025 tax computation worksheets. A frozen set of default results catches any unintended change.
- Exchange rates are the European Central Bank euro reference rates (snapshot of 30 Sept 2026), and you can type your own.
What KeptOffer is not
It is a planning tool. It is not payroll software, not a tax return, and not advice for your personal situation. It covers employment income and the items listed on each page; anything else (investment income, other credits and deductions, other states and provinces) is outside it, and each page says what is not included.
KeptOffer is published by KeptOffer. Corrections are welcome at contact@keptoffer.com and are logged on the changes page with the registry version.
United States: rules (registry v1.0.0, reviewed 2026-09-30)
| Rule | Status | Source |
|---|---|---|
| Marginal rates for tax year 2026 | Confirmed | IRS |
| Standard deduction 2026: $16,100 single, $32,200 MFJ | Confirmed | IRS |
| 401(k) deferral limit $24,500; catch-up $8,000 at 50+ | Confirmed | IRS |
| Contribution and benefit base 2026 $184,500 | Confirmed | SSA |
| OASDI employee rate 6.2% | Confirmed | SSA |
| Medicare employee rate 1.45% | Confirmed | SSA |
| Additional Medicare Tax 0.9% over $200,000 single / $250,000 MFJ (statutory, not indexed) | Assumption: Additional Medicare thresholds are statutory; no 2026 snapshot yet. | IRS |
| FTB 2025 Schedules X and Y | Assumption: California 2026 brackets are published late in the year; 2025 FTB brackets used (2026 indexation adds a few dollars). | FTB |
| 2025 standard deduction $5,706 / $11,412 | Assumption: 2025 California standard deduction used for 2026. | FTB |
| Personal exemption $153 each; AGI limitation $252,203 / $504,411 | Assumption: 2025 exemption credit used; phase-out modelled as $6 per $2,500 of AGI over the limit, per exemption. | FTB |
| Behavioral Health Services Tax: 1% of taxable income over $1,000,000 (Form 540 line 62) | Confirmed | FTB |
| SDI withholding rate 2026 1.3%, no wage ceiling | Confirmed | EDD |
| 2026 rates 3.9/4.4/5.15/5.4/5.9% (NYS-50-T-NYS 1/26, Chapter 59 of 2025 Part A); thresholds and upper rates from the 2025 IT-201 schedules | Confirmed | NY DTF |
| NY standard deduction $8,000 single / $16,050 MFJ | Confirmed | NY DTF |
| Tax computation worksheets for NYAGI over $107,650: benefit of lower rates recaptured over $50,000 bands | Confirmed | NY DTF |
| New York City resident tax rate schedule | Confirmed | NY DTF |
| PFL 0.388% of wages, max $354.53 (2025) | Assumption: 2026 Paid Family Leave rate not yet on the official page; 2025 rate and cap used. | NY Paid Family Leave |
Sources
- IRS: IRS releases tax inflation adjustments for tax year 2026
- IRS: 401(k) limit increases to $24,500 for 2026
- SSA: Contribution and benefit base
- FTB: 2025 California Tax Rate Schedules
- FTB: 2025 Form 540, standard deduction and exemption credits
- EDD: Contribution Rates, Withholding Schedules — SDI 2026
- NY DTF: NYS-50-T-NYS (1/26) New York State Withholding Tax Tables and Methods
- NY DTF: 2025 Instructions for Form IT-201 (rate schedules, recapture worksheets, NYC schedule, standard deduction)
- NY Paid Family Leave: Paid Family Leave: cost
United Kingdom: rules (registry v1.0.0, reviewed 2026-09-30)
| Rule | Status | Source |
|---|---|---|
| Personal Allowance £12,570 | Confirmed | GOV.UK |
| PA down £1 for every £2 of adjusted net income above £100,000 | Confirmed | GOV.UK |
| basic 20% to £50,270; higher 40%; additional 45% over £125,140 | Confirmed | GOV.UK |
| starter 19% £12,571–£16,537; basic 20% to £29,526; intermediate 21% to £43,662; higher 42% to £75,000; advanced 45% to £125,140; top 48% | Confirmed | GOV.UK |
| Primary threshold £12,570 | Confirmed | GOV.UK |
| Upper earnings limit £50,270 | Confirmed | GOV.UK |
| Employee Class 1: 8% PT–UEL, 2% above | Confirmed | GOV.UK |
| Plan 1 £26,900 · Plan 2 £29,385 · Plan 4 £33,795 · Plan 5 £25,000 | Confirmed | GOV.UK |
| 9% over the threshold (lowest threshold if on several plans) | Confirmed | GOV.UK |
| Postgraduate Loan £21,000 | Confirmed | GOV.UK |
| 6% over the threshold | Confirmed | GOV.UK |
| 1% of Child Benefit for every £200 over £60,000; all of it over £80,000 | Confirmed | GOV.UK |
| 1% per £200 | Confirmed | GOV.UK |
| £27.05 eldest, £17.90 each other child | Confirmed | GOV.UK |
| annual = weekly × 52 | Assumption: Child Benefit annualised as 52 weekly payments. | GOV.UK |
| relief at source: provider claims 20% and adds it to the pot | Confirmed | GOV.UK |
Sources
- GOV.UK: Income Tax rates and Personal Allowances
- GOV.UK: Scottish Income Tax: 2026 to 2027 rates
- GOV.UK: Rates and thresholds for employers 2026 to 2027
- GOV.UK: Repaying your student loan: what you pay
- GOV.UK: High Income Child Benefit Charge
- GOV.UK: Child Benefit: what you'll get
- GOV.UK: Tax on your private pension: pension tax relief
Australia: rules (registry v1.0.0, reviewed 2026-09-30)
| Rule | Status | Source |
|---|---|---|
| Resident tax rates 2026–27 | Confirmed | ATO |
| $700; −5c over $37,500; $325 −1.5c over $45,000 (nil from $66,667) | Confirmed | ATO |
| Medicare levy of 2% | Confirmed | ATO |
| singles $28,011 / $35,013 (2025–26 table) | Assumption: 2026–27 low-income Medicare thresholds not yet published; 2025–26 thresholds used. | ATO |
| MLS single thresholds 2026–27: $105,000 / $123,000 / $164,000 | Confirmed | ATO |
| Table 1: 2026–27 marginal repayment thresholds | Confirmed | ATO |
| SG 12.00% from 1 July 2025 | Confirmed | ATO |
| Maximum contribution base 2026–27 $270,830 | Confirmed | ATO |
| General concessional contributions cap $32,500 from 1 July 2026 | Confirmed | ATO |
| Rule | Status | Source |
|---|---|---|
| From 1 July 2027 the 15% rate is reduced to 14% (law); other thresholds unchanged | Confirmed | ATO |
| $700; −5c over $37,500; $325 −1.5c over $45,000 (nil from $66,667) | Confirmed | ATO |
| Medicare levy of 2% | Confirmed | ATO |
| singles $28,011 / $35,013 (2025–26 table) | Assumption: 2027–28 low-income Medicare thresholds not published; 2025–26 thresholds used. | ATO |
| MLS single thresholds 2026–27: $105,000 / $123,000 / $164,000 | Assumption: 2027–28 MLS thresholds not published; 2026–27 thresholds used. | ATO |
| Table 1: 2026–27 marginal repayment thresholds | Assumption: 2027–28 HELP thresholds not published (indexed each year); 2026–27 thresholds used. | ATO |
| SG 12.00% from 1 July 2025 | Confirmed | ATO |
| Maximum contribution base 2026–27 $270,830 | Assumption: 2027–28 maximum contribution base not published; 2026–27 used. | ATO |
| General concessional contributions cap $32,500 from 1 July 2026 | Assumption: 2027–28 concessional cap not published; $32,500 used. | ATO |
Sources
- ATO: Tax rates – Australian residents
- ATO: Personal income tax – new tax cuts for every Australian taxpayer
- ATO: Low income tax offset
- ATO: Medicare levy reduction for low-income earners
- ATO: Medicare levy surcharge income, thresholds and rates
- ATO: Study and training loan repayment thresholds and rates
- ATO: Super guarantee
- ATO: Contributions caps
Canada: rules (registry v1.0.0, reviewed 2026-09-30)
| Rule | Status | Source |
|---|---|---|
| 2026 federal: 14% / 20.5% / 26% / 29% / 33% | Confirmed | CRA |
| non-refundable credits at the lowest federal rate (14% for 2026) | Confirmed | CRA |
| BPA $16,452, reduced to $14,829 between $181,440 and $258,482 | Confirmed | CRA |
| CEA: lesser of $1,501 and employment income | Confirmed | CRA |
| YMPE $74,600, exemption $3,500, 5.95% (base 4.95% credit + first additional 1% deduction) | Confirmed | CRA |
| CPP2 4% between YMPE and YAMPE $85,000 (max $416), fully deductible | Confirmed | CRA |
| MIE $68,900, 1.63% (max $1,123.07) | Confirmed | CRA |
| Chart 2 — 2026 Ontario rates | Confirmed | CRA |
| Ontario non-refundable credits at 5.05% | Confirmed | CRA |
| Ontario basic personal amount $12,989 | Confirmed | CRA |
| 20% of basic Ontario tax over $5,818 + 36% over $7,446 | Confirmed | CRA |
| tax reduction: 2 × $300 minus Ontario tax before reduction | Confirmed | CRA |
| OHP by taxable income: rows [upTo, base, rate over previous edge, cap] | Confirmed | CRA |