Pension salary sacrifice in UK payroll: contract first, then pay bases
A UK employer wants to offer pension salary sacrifice, and payroll is asked to switch it on from next month. The tempting shortcut is to relabel the existing employee pension deduction. That does not work. A valid salary sacrifice changes the employee's contractual entitlement to cash pay before that pay is earned, and the employer then pays the sacrificed amount into the pension as an employer contribution. An employee contribution through an eligible net-pay arrangement reduces pay for PAYE but leaves National Insurance earnings unchanged. This article covers registered private-sector workplace pensions in the tax year from 6 April 2026 to 5 April 2027.
What makes the change valid
HMRC's salary sacrifice guidance requires the employee to agree to change the employment contract so that they are entitled to less cash pay. The new entitlements must be clear, and the change cannot operate retrospectively. Cash earnings after the sacrifice cannot fall below the National Minimum Wage, so payroll needs a cap or control that checks each pay reference period.
HMRC's National Insurance Manual says that a formal agreement giving up rights to earnings in exchange for employer contributions to a registered pension can mean no NIC liability on those contributions under current rules. The contract variation carries this treatment. A payslip label alone does not prove a sacrifice exists.
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How net pay differs
Under a net-pay arrangement, the employee's own pension contribution comes out of pay before income tax. HMRC's 2026 to 2027 employer further guide confirms that this reduces pay for PAYE, not for National Insurance. The National Insurance Manual adds that NICs on employee pension contributions are worked out on gross earnings before the deduction. Net pay therefore gives income tax relief with no matching NIC relief.
Not every scheme uses net pay. Confirm how your scheme collects employee contributions before comparing the two routes.
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Hypothetical: £150 a month two ways
Hypothetical: a private-sector employee has a gross cash salary of £3,000 a month, no other taxable or NI items, and belongs to a registered workplace pension. The comparison sets a £150 employee contribution through an eligible net-pay scheme against a valid £150 salary exchange agreed before the earnings become due. Personal allowances and tax rates are ignored. Any ordinary employer contribution stays the same and is left out. Pay after the change remains above the relevant hourly minimum wage.
Under the exchange, payroll must not also deduct £150 from the employee, and the pension provider should not be asked to add relief at source to the same employer contribution. The figures show pay bases only. They do not promise a particular take-home pay or employer saving.
| Item | Net-pay contribution | Salary exchange |
|---|---|---|
| Contractual cash salary | £3,000 | £2,850 |
| Pay for PAYE | £2,850 | £2,850 |
| NI earnings | £3,000 | £2,850 |
| Pension payment | £150 employee deduction | £150 additional employer contribution |
Reference pay and statutory payments
Some schemes base contributions and earnings-related benefits on notional pay before the sacrifice. HMRC's guidance allows this where the arrangement specifies it, and says employers should confirm the arrangement with the pension provider. Sacrifice can also affect statutory payments and contribution-based benefits. Contributions still need checking against the relevant pension tax limits, which this article does not calculate.
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The plan for April 2029
On 4 December 2025 the government published plans for a measure that would apply from 6 April 2029. Salary or bonus sacrificed for pension contributions above a £2,000 annual limit would attract employee and employer Class 1 NICs. Income tax treatment, and NIC treatment of ordinary employer pension contributions, would stay as they are. This is a future measure, not a cap on 2026 to 2027 payroll, and the current NIC position should not be presented to staff as permanent.
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Before the first changed payday
Match three things before the first payday under the new terms: the contract effective date, the PAYE and NIC pay bases in payroll, and the provider's classification of the payment as an employer contribution.
- Employee consent and the varied contract, dated before the entitlement arises
- Payslips from before and after the change showing taxable and NIC pay
- An hourly minimum wage check for each pay reference period
- The provider agreement, employer contribution schedule and remittance reconciliation
- A written policy on reference salary, employer match, overtime and statutory pay