How the calculator works

Choose the right year and region

The main calculator supports 2026/27 and 2025/26. Income Tax uses the selected year’s standard Personal Allowance and employment-income bands. Scotland has separate bands; Wales and Northern Ireland use the same employment-income rates as England in this model. We do not infer your tax region from your student loan plan.

Personal Allowance and taxable bands

The standard allowance is £12,570. It reduces by £1 for each £2 of adjusted net income over £100,000. We apply band widths to taxable income after the allowance, rather than subtracting gross-salary table boundaries. That distinction matters in the allowance-taper range.

National Insurance and pay periods

The annual comparison applies the standard employee rates of 8% and 2% to annualised thresholds. Actual NI is normally calculated for each pay period and can differ for bonuses, irregular pay, directors or other categories. Monthly net is the annual estimate divided by 12; four-weekly net is divided by 13. These are averages, not a payroll simulation.

Pension assumptions

Select full salary or qualifying earnings as the contribution basis. Qualifying earnings use the model’s £6,240 lower bound and £50,270 upper bound. Confirm your scheme’s own pensionable-pay definition. The percentage represents the gross pension contribution, including the provider’s top-up for relief at source.

Salary sacrifice reduces the salary used for tax, NI and loan repayments. Net pay reduces taxable pay. Relief at source deducts 80% of the gross contribution from pay and estimates eligible extra Income Tax relief. That extra relief may need a claim: the annual result can therefore be higher than cash received through payslips before the refund or code adjustment. Employer contributions and allowance charges are not modelled.

Student loans

Undergraduate plans use one 9% deduction over the lowest threshold of the selected plans. A postgraduate loan adds a separate 6% deduction. Plan 5 is available from 2026/27. This is an annual comparison without loan-balance caps; payroll uses pay-period thresholds and whole-pound rounding. Check your repayment start date before selecting a plan.

What we leave out

Custom tax codes, tax already paid earlier in the year, taxable benefits, other income, Marriage Allowance, expenses, Child Benefit charges, benefit entitlement, pension allowance charges and self-employment are outside the main calculator. Specialist tools can have narrower assumptions stated on their pages.

Verification and corrections

The calculation engine has regression checks for allowance tapering, Scottish bands, pension methods, loan combinations and boundary cases. Worked guide tables are generated from that same engine. Tests establish consistency with the cases checked; they do not turn an annual estimate into an exact payslip.

Sources: Income Tax, Scottish Income Tax, NI, student loans, pension relief and workplace contributions. If you find a discrepancy, send a correction.

Last updated 8 October 2026.