Which arrangement gives the most take-home pay?

Salary sacrifice, for the same amount reaching the pension, because it is the only one that also reduces National Insurance and student loan repayments. Net pay is next, and relief at source leaves you worst off in the short term if you pay above the basic rate and never claim the remainder.

Can I choose my arrangement?

Usually not — the employer picks the scheme. Some employers do offer salary sacrifice as an option, so it is worth asking, but you cannot switch unilaterally.

I am on relief at source and pay higher-rate tax. What do I do?

Claim the difference from HMRC, through a Self Assessment return if you file one, or by contacting HMRC if you do not. Claims can normally be backdated for several years, so it is worth checking earlier tax years as well.

Does auto-enrolment use a particular arrangement?

Auto-enrolment schemes run on either net pay or relief at source depending on the provider — which is precisely why so much unclaimed higher-rate relief exists. Salary sacrifice is a separate arrangement an employer has to offer deliberately.

The Three Pension Arrangements, and Why They Are Not Interchangeable

Two people can pay the same percentage into the same pension and end up with different take-home pay, different National Insurance, and different student loan deductions. The reason is that UK workplace pensions run on three different arrangements — salary sacrifice, net pay, and relief at source — and they differ in what they reduce, not just in paperwork. One of them leaves part of your relief unclaimed unless you go and ask for it.

The take-home pay calculator asks which arrangement you are on, because the answer changes the result — pick yours and compare.

Salary Sacrifice: Your Contractual Salary Actually Falls

Under salary sacrifice you formally give up part of your salary in exchange for an employer pension contribution. Because your contractual pay is genuinely lower, everything calculated from pay falls with it: income tax, National Insurance, and student loan repayments. That is why, for the same amount landing in the pension, salary sacrifice usually leaves the most in your bank account — the National Insurance saving is real money that the other two arrangements do not give you. The limit is that sacrifice cannot reduce your pay below the National Minimum Wage; an employer must refuse an arrangement that would. It can also affect anything else calculated from salary, such as mortgage affordability assessments or death-in-service cover, which is worth checking before you increase it sharply.

Net Pay: Taken Before Tax, But Not Before National Insurance

In a net pay arrangement your contribution comes out of gross pay before income tax is worked out, so tax relief arrives immediately and in full at whatever rate you pay — nothing to claim. But your contractual salary is unchanged, so National Insurance and student loan repayments are still calculated on the full amount. This is the middle option: the tax relief is as good as salary sacrifice, the National Insurance saving is absent. The payslip signature is a contribution deducted before the tax line, with taxable pay lower than gross pay.

Relief at Source: The One Where You Have to Claim

Under relief at source your contribution is taken from pay that has already been taxed. Your pension provider then reclaims basic-rate relief from HMRC and adds it to your pot automatically. For a basic-rate taxpayer that completes the picture. For anyone paying above the basic rate it does not: the remainder is not added to your pension and does not appear on your payslip. You have to claim it, through a tax return or by contacting HMRC, and it comes back to you as cash or an adjusted tax code rather than as pension. A great many higher-rate taxpayers never claim it, because nothing in the process tells them they should. If your payslip shows a pension deduction taken after tax, this is you — and it is worth checking whether you have claimed for previous years too.

How to Tell Which One You Are On

You do not need to know the industry terminology, only how to read your payslip. If your gross pay itself is lower than your contractual salary and there is an employer pension line, that is salary sacrifice. If gross pay is unchanged but taxable pay is lower than gross, that is net pay. If the pension deduction sits below the tax and National Insurance lines, so your taxable pay equals your gross pay, that is relief at source. If you cannot tell, payroll can answer in one email — and given that one of the three requires action from you, it is a question worth asking rather than assuming.