Extra pension vs the real drop in take-home — NI, student loan and the £100k tax trap
ΔTax + ΔNI + ΔStudent loansacrifice + employer NI pass-back
Results always show both systems side by side. This just marks “your” column.
Bonus, taxable benefits, other earnings that sit in the £100k taper. Leave 0 if unsure.
Modelled on headline salary and assumed unchanged when you sacrifice more.
= £833 / month
Employer NIC is 15% above £5,000. Many employers keep this saving; set 100 if they add all of it to your pension.
Your entries are stored in this browser only and restored next time you open the page.
Each row is a different extra annual sacrifice. Highlighted row is your current extra. Green row is the amount that restores the full personal allowance, if you are in the trap.
| Extra sacrifice | Pension in | Drop rUK | Drop Scotland | Relief rUK | Relief Scot | ANI | Trap? |
|---|---|---|---|---|---|---|---|
| Adjust inputs to see results | |||||||
This free UK tool shows what extra workplace pension via salary sacrifice is really worth. It compares the extra amount landing in your pension with the actual fall in take-home pay after Income Tax, employee National Insurance and student loan — and it flags the £100,000 personal allowance taper. England/Wales/NI and Scottish Income Tax are calculated side by side on 2026/27 rates.
take-home drop ÷ extra pension in
If you sacrifice £10,000 and take-home only falls by £3,800, each £1 in the pension cost you 38p. The other 62p is tax, NI and (if applicable) student loan you no longer pay.
Adjusted net income above £100,000 reduces the £12,570 personal allowance by £1 for every £2. The allowance is zero at £125,140. Across that band the effective income-tax rate is 60% (62% including 2% NI). Click Clear the £100k trap to set extra sacrifice so ANI returns to £100,000.
National Insurance and student loan rules are UK-wide. Scottish Income Tax uses six bands (19%, 20%, 21%, 42%, 45%, 48%) so the take-home drop — and therefore the effective relief — differs. The chart plots extra pension against both take-home drops as you increase sacrifice.
Goal: see the 42% relief (40% tax + 2% NI) on extra sacrifice.
On a slice still above the £50,270 NI upper earnings limit, each £1 sacrificed typically costs about 58p in take-home (42% relief) before any pass-back.
Goal: convert 60% tax into pension instead of losing personal allowance.
The first £4,500 of extra sacrifice restores the tapered allowance (about 60% income-tax effect + 2% NI). Sacrifice beyond that earns normal higher-rate relief. Use “Clear the £100k trap” to land exactly on £100,000 ANI.
Goal: include the extra 9% payroll deduction in the “real” take-home drop.
Above the Plan 2 threshold (£29,385 in 2026/27) salary sacrifice also reduces student loan by 9% of the sacrificed slice. That is a cash-flow saving now; it is not a write-off of the loan balance.
Not professional advice: This calculator is an educational estimate. It is not tax, pension or regulated financial advice. Payroll, tax codes and scheme rules vary. Speak to a qualified adviser and check with your employer’s pension / payroll team before changing contributions.
Assumptions: Category A National Insurance, standard personal allowance, no Blind Person’s Allowance or Marriage Allowance, employer contribution held constant on headline salary, student loan based on post-sacrifice PAYE earnings, relief-at-source modelled with basic-rate (20%) scheme relief only. High Income Child Benefit Charge, Tax-Free Childcare and free-hours cliffs are not calculated. Defined-benefit accrual, tapered annual allowance, MPAA and carry-forward are not modelled in full.
Other real-world effects: Salary sacrifice can affect mortgage affordability, life cover, statutory pay and must not take cash pay below National Minimum / Living Wage. From April 2029, UK policy is expected to apply National Insurance to salary-sacrificed pension contributions above £2,000 a year — this 2026/27 engine does not apply that future rule.
Student loans: A lower payroll deduction is a cash-flow benefit. The underlying loan is unchanged except to the extent that you repay less now (and may therefore repay more later or write off more at the end of the term).
Please email suggestions and bug reports to: salarysacrificeoptimiser@personalfinances.me, thank you.