When are payments on account normally due?

They are normally split into two instalments due on 31 January and 31 July. Each is usually half the relevant previous-year amount, but HMRC's statement is authoritative.

When might payments on account not apply?

HMRC says they are generally not required when the relevant amount is below £1,000 or more than 80% of the assessed tax was paid outside Self Assessment. Select no only after checking your account or the rule.

Does the profit input mean turnover?

No. Enter forecast taxable profit after allowable business expenses and accounting adjustments, not gross sales. Confirm the figure with records or accounting software.

What is excluded from the reserve?

The tool excludes VAT, Capital Gains Tax, student loans, High Income Child Benefit Charge, voluntary Class 2, partnership allocations, basis-period adjustments and penalties or interest.

Self-Employed Tax Set-Aside Calculator UK 2026/27

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Self-Employed Tax Set-Aside Planner · UKTax & Duties

Example result based on the prefilled values.

Estimated Income Tax

£7,486.00

Estimated Class 4 NI

£2,245.80

Current-Year Self Assessment Amount After Tax Deducted

£9,731.80

Remaining Balancing Payment

£9,731.80

Each Modelled Payment on Account

£4,865.90

January Cash Target

£14,597.70

July Cash Target

£4,865.90

Monthly Current-Year Reserve

£810.98

Reserve as Share of Profit

19.46%

Continue your plan

Useful next calculations

Related to this calculation

Use the Self-Employed Tax Calculator

Continue with the related tax & salary question this result raises.

Use the Cash Flow Calculator

Continue with the related business question this result raises.

Rates & sources2026/27

2026/27 Income Tax and Class 4 NI reserve estimate. Payments on account are shown as advance cash requirements and are not added to the tax liability.

Class 4 main rate6%

Class 4 additional rate2%

Payment-on-account instalmentsnormally 50% each

Normal due dates31 January / 31 July

Source: HMRC — self-employed National Insurance — source checked for 2026/27.

When to use this calculator

Before accepting a pay change, bonus, pension contribution, or salary-sacrifice option.
When you want to compare employed, self-employed, or dividend-based income scenarios.
When you need a simple take-home estimate before running payroll or filing returns.
When you are approaching the £100,000 income level and want to understand the personal allowance taper effect.
When you are planning a salary sacrifice arrangement and need to see the net pay impact before agreeing terms.

A realistic UK planning example

Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.

Forecast taxable self-employed profit (£)

50000

Other non-savings taxable income (£)

£35,000

Gross pension contributions + grossed-up Gift Aid (£)

£35,000

Income Tax already deducted at source (£)

£35,000

After entering these figures, review estimated income tax, estimated class 4 ni and current-year self assessment amount after tax deducted together rather than in isolation — each metric tells a different part of the story. Then rerun the tool with one input adjusted to see which variable has the biggest effect on all three outputs before you settle on a plan.

How to read your results

Estimated Income Tax

Review this figure alongside your gross income so you can understand the true cost of deductions and plan around any thresholds before the tax year closes. If the figure looks higher than expected, check whether any pension or gift-aid contributions could reduce your taxable income.

Estimated Class 4 NI

Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.

Current-Year Self Assessment Amount After Tax Deducted

Remaining Balancing Payment

Each Modelled Payment on Account

January Cash Target

July Cash Target

Monthly Current-Year Reserve

Reserve as Share of Profit

Method & assumptionsAuthoritative sources

This planner estimates 2026/27 Income Tax on the profit and other non-savings income entered, then adds Class 4 National Insurance when selected and subtracts tax already deducted at source. Payments on account already made reduce the remaining balancing payment.

The monthly reserve covers the estimated current-year Self Assessment amount. When payments on account are selected, the January cash target adds one half of that amount as a proxy for the next year's first payment; the July target shows the second half. Those advances are not counted as extra tax.

HMRC uses the filed previous-year return and detailed relevant-amount rules. This estimate excludes VAT, student loans, CGT, HICBC, Class 2 choices, penalties, interest and many reliefs. Use the HMRC statement and reduce payments on account only when there is a reasonable basis, because an excessive reduction can attract interest.

Common mistakes

!Entering gross income when you really want take-home pay, or vice versa.
!Ignoring pension contributions, deductions, or local tax rules that change the result.
!Comparing monthly and annual figures without standardising them first.
!Overlooking the National Insurance threshold changes that apply mid-year when rates or bands are adjusted in a Budget.
!Assuming a salary sacrifice benefit reduces take-home pay by the full gross amount, rather than only the after-tax cost.

What to do next

Check the same scenario with related pay or deduction calculators to see the full picture.
Keep a copy of the assumptions you used so you can compare next tax year or pay period accurately.
Read the related guides below if you are choosing between multiple income or deduction options.
If you are self-employed, run the self-employment tax calculator alongside this result to compare the net position against employed income.
Check whether increasing your pension contribution by even one or two percent changes the take-home significantly — use the pension calculator next.

Frequently asked

No. They are advance payments towards the next Self Assessment bill. The planner shows them separately because they can increase the cash due in January even though they are credited against the following liability.

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