NHS Back Pay & Arrears Calculator

Because pay awards and pay-point increments both have a fixed effective date set by national agreement or your own incremental date, but the actual administrative work of confirming, funding and reprogramming every affected pay point in a trust's payroll system (ESR) genuinely takes time — often weeks or months. Employers are expected to apply arrears back to the correct effective date once the new rate is live, so a delay in your payslip catching up doesn't mean you lose the difference — it means it should arrive as a lump sum alongside your new ongoing rate.

In principle it should happen automatically once the new rate is confirmed and loaded into payroll — you shouldn't need to submit a claim for a standard, nationally agreed backdated pay award or a routine incremental date. If a genuinely long time has passed since the new rate should have started and you still see no change or arrears on your payslip, that's a reasonable thing to raise directly with your trust's payroll team, since implementation timelines can vary between employers even for the same nationally agreed change.

No, and deliberately so — you enter your own old salary, new salary (or a percentage increase), and the two dates yourself. This keeps the tool accurate for ANY backdated pay scenario — a national pay award, a pay-point increment, a banding review outcome, a job evaluation result — rather than tying it to one specific year's award, which can change. For FrontlinePay's sourced discussion of the current year's confirmed pay award, see the NHS Pay Rise guide linked below.

Because UK Income Tax and National Insurance are progressive — the rate on each pound you earn depends on your TOTAL income for the year, and a lump sum arrears payment sits on top of your normal salary in that stack, not underneath it. If your normal salary already uses up your personal allowance and part of the basic rate band, a large enough arrears payment can genuinely push part of itself into a higher marginal rate than the rest of your income — this calculator estimates that by comparing your take-home at your normal salary against your take-home at your normal salary plus the arrears, so the difference reflects the real marginal rate the lump sum attracts.

No — moving into a higher marginal tax band because of a one-off lump sum affects the tax on that extra income only, for that tax year; it doesn't change the rate applied to your ordinary ongoing salary once the lump sum has been paid. It's also worth knowing that PAYE in the UK is normally calculated cumulatively across the tax year with the same employer, which means an unusually large single payslip can sometimes result in MORE tax being deducted from that one payslip than turns out to be correct for the year as a whole — and that often self-corrects through slightly lower deductions in your following payslips, or via HMRC reconciliation, rather than being a genuine permanent extra cost. If a large arrears payment falls right at the end of a tax year, or coincides with a tax code change or a second job, it's worth double-checking with HMRC that everything reconciled correctly.

It's a close, methodologically sound estimate, not a payslip guarantee. It's calculated by running your normal new salary through FrontlinePay's tax/NI/pension engine, then running your normal new salary PLUS the arrears lump sum through the same engine, and taking the difference — which correctly captures progressive tax and NI bands and NHS Pension contribution tiers. It can't capture your specific tax code, whether the arrears is paid in the same tax year it was earned, salary sacrifice arrangements, or exactly how your trust's payroll system times and splits the payment. Treat it as a strong planning estimate, and check your actual payslip once the arrears lands.

Either — toggle to 'Enter a % increase' if you know the percentage but not the resulting salary figure, and the calculator works out the new annual salary for you from your old salary. Toggle back to 'Enter new salary' if you already know both figures exactly, for example from a confirmed pay-point value on the Agenda for Change scale.

This calculator models a straightforward basic-pay-rate change between two dates — it doesn't separately model changes to High Cost Area Supplement, unsocial hours enhancements, or overtime rates, since those move independently and depend on your actual rota for the backdated period, not just a flat annual difference. If your increase affects more than basic pay, use the old and new BASIC salary figures here for the basic-pay arrears, and check any supplementary payments separately with your trust's payroll team.

Yes — enter your ACTUAL old and new annual salary (already reflecting your contracted part-time hours), not a full-time-equivalent figure, and the day-count and £ maths will be correctly scaled to your real pay automatically, since it's working from your real annual salary throughout rather than a separate hours-based pro-rata calculation.

It's a straightforward calendar-day count between your entered effective date and the date you're calculating arrears up to (inclusive), converted to a daily pay difference using a standard 365.25-day year. It doesn't attempt to model your trust's specific pay-period boundaries or exactly which payslip the arrears will appear on — for that level of precision, your trust's payroll team can confirm exactly how they've calculated your specific arrears once it's processed.