The short answer
Learn how the UK Pension Efficiency Calculator compares salary sacrifice, Net Pay, Relief at Source, employer matching, Annual Allowance and carry-forward.
The Pension Efficiency Calculator compares how a UK pension contribution may look under three methods: salary sacrifice, Net Pay and Relief at Source. It also models employer matching, possible National Insurance effects, Annual Allowance and carry-forward inputs, and a simplified long-term growth scenario.
The result is not a tax refund, payslip or pension-provider quote. The contribution method, tax band, relevant earnings, employer policy, pension input amount, previous contributions and eventual withdrawal rules all matter. The calculator is most useful when it shows which assumption is driving the result and which fact still needs confirmation.
This guide is distinct from the UK Pension Annual Allowance guide, the Pension Carry Forward guide and the Salary Sacrifice guide. Those pages explain individual rules; this page explains how to interpret the combined calculator scenario.
Net cost depends on method
Allowance is not the same as relief
Employer match can dominate
What the calculator is trying to answer
The tool asks a practical question: under these salary, contribution, tax and employer assumptions, how much pension value might be created and what is the modelled cash cost? It is not asking which pension product is best or whether a contribution is suitable.
Enter the salary, contribution rate, age, employer match, available carry-forward and contribution method. The result can show:
- the gross employee contribution;
- an employer contribution under the entered match assumption;
- an illustrative Income Tax and National Insurance effect;
- a possible net-pay comparison;
- Annual Allowance headroom and carry-forward context;
- a projected value under a stated growth assumption.
Before trusting the output, identify whether the model matches your situation. The tool is a simplified rUK model and does not automatically determine Scottish Income Tax, your adjusted income, the pension input amount for a defined-benefit scheme, the exact scheme charge or your employer’s payroll rules.
The three contribution methods
Salary sacrifice
Salary sacrifice is a contractual change in which an employee gives up part of cash salary and the employer pays the amount into the pension or provides another benefit. GOV.UK guidance explains that it can affect PAYE and National Insurance. The employee’s contractual cash salary, taxable pay and pay-related benefits can change.
The calculator may show an employee National Insurance saving under salary sacrifice. That is a scenario, not a guaranteed outcome. The exact result depends on the contribution, earnings band, tax year, contract, payroll and whether the employer shares any secondary National Insurance saving. An employer is not automatically required to pass its saving to the employee.
Salary sacrifice can also affect mortgage evidence, statutory pay, salary-linked benefits or other workplace calculations. Ask the employer what pensionable pay, bonus, overtime, life cover and statutory payments are based on before choosing the method.
Net Pay
Under a Net Pay arrangement, the employee contribution is deducted from gross pay before Income Tax is calculated, subject to the scheme and payroll rules. The visible payslip effect can differ from salary sacrifice because National Insurance and the contractual salary may be treated differently.
Do not assume that every workplace pension uses Net Pay. Check the payslip, scheme documents and employer explanation. If the calculator compares Net Pay with salary sacrifice, the result is a structured illustration of the entered assumptions rather than evidence of how your employer must process the contribution.
Relief at Source
With Relief at Source, the employee generally pays a net contribution and the pension provider claims basic-rate tax relief, subject to the conditions. A higher-rate taxpayer may need to claim additional relief through the appropriate process. The cash flow and tax-return treatment can therefore look different from salary sacrifice or Net Pay.
The calculator may display a lower immediate relief assumption for Relief at Source. That does not mean the contribution is permanently taxed at basic rate; it means additional relief may need to be claimed if eligible. Confirm the provider’s method and use current GOV.UK guidance for the actual claim.
Annual Allowance is not a tax-relief percentage
For 2026/27, GOV.UK pension rates guidance lists a standard Annual Allowance of £60,000. Annual Allowance measures pension input across relevant arrangements and can include employer contributions. It is not simply the amount an employee personally pays, and it is not the same as the amount on which an individual can claim tax relief.
The available allowance may be affected by the tapered Annual Allowance or the Money Purchase Annual Allowance. The calculator can accept assumptions for these conditions, but it cannot determine eligibility from salary alone. Adjusted income, threshold income, flexible access history and pension input statements may be needed.
If the model shows an excess, do not calculate the charge by multiplying the excess by one tax rate. The tax charge depends on the applicable rules, taxable income, available carry-forward and the pension input calculation. HMRC’s pension savings tax-charge guidance should be checked for the relevant tax year.
Carry-forward from previous years
Subject to the conditions, unused Annual Allowance from the previous three tax years may be carried forward. The calculation depends on the allowance in each year, pension input amounts, membership of a registered pension scheme and any tapered or MPAA rules.
Enter carry-forward only when you have reliable records. A rough guess can make the model show headroom that does not exist. Look for pension input statements, scheme records and prior tax information. A defined-benefit scheme can create a pension input amount that is not equal to the employee’s cash contribution.
Carry-forward increases possible Annual Allowance capacity; it does not automatically create a personal tax-relief entitlement above relevant earnings. It also does not remove scheme limits, affordability issues or the need to confirm how an excess is handled.
Employer matching and employer NI pass-back
Employer matching can be the most decision-relevant part of the model. Enter the actual match rate and the contribution threshold from the scheme rules. A hypothetical 5% match is not evidence that your employer offers 5%, and a match may apply only to pensionable salary or only up to a cap.
Check:
- the contribution percentage needed to receive the full match;
- whether the employer matches the employee’s full contribution or only a portion;
- the salary definition used;
- whether the match is immediate or subject to vesting;
- what happens after a promotion, bonus, unpaid leave or reduced hours;
- whether employer contributions count toward Annual Allowance;
- whether the employer shares any National Insurance saving.
The calculator’s pass-back switch is an employer-policy assumption. Treat it as a sensitivity input, not a contractual entitlement. Compare a zero pass-back case with the employer’s written policy.
The modelled net cost
The displayed net cost is a planning expression, usually based on the gross contribution minus the modelled Income Tax and National Insurance effect. It is not necessarily the amount by which your bank balance changes. Payroll timing, tax codes, relief method, student loan, benefits, Child Benefit, pension limits and salary-linked calculations can all affect take-home pay.
Use a simple table to interrogate the output:
| Output | What it means | What it does not prove |
|---|---|---|
| Gross pension contribution | Amount entering under the scenario | That the provider accepts it |
| Modelled tax relief | Input-based Income Tax effect | Your final tax liability |
| NI effect | Simplified employee or employer assumption | An employer pass-back entitlement |
| Net cost | Scenario contribution less modelled savings | Exact payslip change |
| Projected fund | Growth model under stated inputs | Guaranteed retirement value |
If the result differs from your payslip, investigate the method and inputs before assuming the calculator is wrong. The scheme’s payroll treatment is the authoritative record for what actually happened.
Relevant earnings and personal relief
Personal tax relief on pension contributions can be limited by relevant UK earnings as well as pension allowances. GOV.UK guidance on private pension contributions should be checked for the type of contribution, relief method and circumstances. A person with low or no relevant earnings cannot assume that a large personal payment receives unlimited relief.
The calculator’s salary field is not a complete relevant-earnings assessment. Other employment, self-employment, taxable benefits, pension income and contribution types can change the real calculation. If you receive income from several sources, treat the model as a first pass only.
MPAA and flexible access
The Money Purchase Annual Allowance can apply after certain flexible access to a defined-contribution pension. For 2026/27, official pension rates guidance lists an MPAA of £10,000. The rule is separate from the normal Annual Allowance and can restrict future money-purchase contributions.
Do not select MPAA merely because you have accessed a pension. Check the exact type and timing of the withdrawal and the provider’s information. If MPAA applies, carry-forward cannot be used to restore the MPAA limit in the same way as normal Annual Allowance capacity.
Growth and retirement outcomes
The calculator projects pension growth under a constant assumption. Actual returns vary, charges reduce the pot, inflation reduces purchasing power and contributions can change. Run a lower, central and adverse scenario. Include a case where the market falls shortly before retirement, because an average return can hide sequence-of-returns risk.
A fund value is not retirement income. Income depends on annuity rates, drawdown, withdrawals, investment performance, longevity and tax. The Lifetime Allowance was abolished, but that does not mean every retirement benefit is tax-free or that lump-sum limits no longer matter.
GOV.UK’s Lump Sum Allowance guidance should be checked for the current rules. The calculator does not create a personal tax-free cash entitlement from a percentage of the projected pot. Previous crystallised benefits and the pension arrangement can matter.
Common mistakes
Treating every method as interchangeable
Salary sacrifice, Net Pay and Relief at Source can produce different payroll and tax outcomes. Confirm the scheme method.
Confusing Annual Allowance with relief headroom
Annual Allowance includes relevant pension input, while personal tax relief has separate relevant-earnings and method conditions.
Assuming employer NI pass-back
The employer may retain or share its saving. Use the written policy, not the calculator default.
Using salary as a proxy for tapered allowance eligibility
Adjusted income and threshold income tests can be required. The calculator cannot determine tapering from one salary figure.
Treating the projection as a recommendation
Growth, charges, access, investment risk and future tax all affect suitability. A larger projected pot is not automatically the right result.
FAQs
What is the UK Pension Annual Allowance for 2026/27?
How does salary sacrifice compare with Relief at Source?
Can I use carry-forward to increase my allowance?
What is the MPAA for 2026/27?
Does an employer match count toward Annual Allowance?
Does salary sacrifice always save National Insurance?
Is the calculator an HMRC calculation?
Bottom line
The UK Pension Efficiency Calculator is useful for comparing contribution methods and making the cash-flow trade-off visible. Start with the real scheme method, employer match and contribution records. Then check Annual Allowance, carry-forward, MPAA, relevant earnings and the retirement withdrawal rules.
Treat salary sacrifice, Net Pay and Relief at Source as different payroll routes, not interchangeable labels. Treat employer NI pass-back as a policy assumption, and treat every growth or net-cost figure as illustrative. For 2026/27, verify the current GOV.UK rules before changing contributions or relying on a projected tax saving.
Official sources
Related Guides
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UK Pension Tax Relief 2026/27 — Net Pay vs Relief at Source
UK pension tax relief for 2026/27: how net pay and relief at source work, when higher-rate taxpayers claim more, annual limits and how to correct a claim.
Lifetime ISA vs Pension UK 2026/27
Compare Lifetime ISA and pension saving for a first home or later life, including the 25% bonus, access rules, tax relief and withdrawal restrictions.
Review notes and assumptions
Reviewed
2026-09-22
Assumptions
- The calculator compares simplified rUK scenarios. Scottish Income Tax, payroll processing, scheme rules, adjusted income, relevant earnings and provider records can change the result.
- The standard Annual Allowance, MPAA, tax bands and other policy values are tax-year-specific and must be checked against current GOV.UK guidance.
- Growth and employer pass-back figures are assumptions, not guaranteed investment returns, employer benefits or a personalised pension recommendation.