Methodology & sources

This tool models the UK income-tax, employee-NI and pension annual allowance interactions for someone planning a corporate exit within a given tax year. It is specifically about exit timing — when to leave and how that interacts with pension structuring of final-year compensation. It is not a general-purpose take-home pay calculator and is not a redundancy/severance calculator.

How the sweep works

You describe your compensation as a timeline: annual base salary, bonus pay dates and amounts, RSU vest dates and market values. The tool sweeps month-end candidate exit dates from 6 April to 5 April. For each candidate it assumes employment ends on that date — salary paid up to then is counted, bonus and RSU events with dates on or before the exit are counted, later events are excluded.

At each candidate exit date the tool also evaluates several pension-contribution strategies in parallel so you can see the full tradeoff: no extra, top up to £100k (to avoid the 60% personal-allowance taper), and max within annual allowance plus 3 years of carry-forward. Add a “custom” number in the form to see a fourth column with your own amount. Each strategy shows the additional contribution required, total tax + NI, and net cash. Cells where the contribution exceeds the annual allowance plus carry-forward are flagged.

What is modelled

Income tax — England & Wales bands for 2026/27. Personal allowance £12,570, tapered £1 per £2 over £100,000 (fully lost at £125,140). Basic rate 20%, higher rate 40%, additional rate 45%.
Employee National Insurance — Class 1: 8% between £12,570 and £50,270, 2% above.
Pension annual allowance — £60,000 for 2026/27. Tapered £1 per £2 of adjusted income over £260,000 (subject to threshold income exceeding £200,000), floor £10,000 at adjusted income ≥ £360,000.
Carry-forward — unused AA from the 3 prior tax years. Current year used first; oldest prior year next; then progressively newer years.
Salary sacrifice — reduces gross taxable salary, cutting both income tax and employee NI. The primary lever for ducking the 60% taper band.
RSU vests — treated as employment income at market value on vest date, with PAYE income tax and Class 1 NI. Section 431 election assumed.

What is NOT modelled

Scotland and Northern Ireland tax bands. (NI bands match E&W; Scottish bands differ.)
Defined benefit pension input amounts. Assume DC schemes only.
Money Purchase Annual Allowance (MPAA) — applies if you've flexibly accessed a DC pot. Not modelled.
LSA / LSDBA (post-LTA lump sum allowances).
Post-vest RSU gain/loss — CGT territory. Out of scope.
Termination payments, statutory redundancy, PILON / PENP, the £30k exemption. Not part of the “leave on your own terms” question.
Cross-tax-year sweep. v1 only sweeps exit dates within the current tax year. To weigh e.g. a late-March vs. early-April exit (where one bonus lands in next year), run the tool twice.
Annual Allowance Charge calculation on excess contributions — the over-allowance amount is flagged but not auto-taxed.
Employer NI savings (don't affect employee take-home).

Simplifying assumptions

Both employee “salary sacrifice” and “RAS” percentages are treated as gross-equivalent sacrifice (i.e. reduce taxable income directly). In real life RAS works via basic-rate-at-source plus higher-rate relief on self-assessment — same end-result on tax due, slightly different cashflow.
Salary is assumed paid in equal monthly instalments from 6 April. Months are counted whole — the first month is “1 month” even if exit is on the 30th of April.
Employer pension contributions are applied to salary actually paid pre-exit at the user's stated percentage.
NI is computed annually on taxable income rather than per pay-period (standard for tax-year planning calculators).
Threshold and adjusted income for AA taper are approximated as: threshold = taxable income after sacrifice; adjusted = threshold + all pension contributions (employee + employer + additional).
The “additional contribution” lever is one annual number; the engine applies it to every candidate exit date and caps it by the sacrificable pool at that date (salary received post existing sacrifice + bonus + RSU value).

Authoritative sources

Disclaimer

This is an educational tool. Tax rules change, edge cases abound, and your actual position depends on the full picture of your tax affairs (foreign income, capital gains, salary-sacrifice eligibility, scheme rules, etc). Verify against HMRC guidance and consult a chartered tax adviser or a regulated financial planner before acting on anything shown here. The author is not a tax adviser.

Privacy

No accounts, no cookies, no server-side storage. Your inputs are encoded in the URL query string; that's where the “state” lives. You can bookmark a scenario, share it, or close the tab and there's nothing to delete.

Data version

Tax-year data file: 2026_27. Last reviewed against gov.uk: 2026-05. Thresholds carried forward under the Autumn Statement 2022 freeze (through 5 April 2028); pension AA unchanged since April 2023.