Self Assessment payments on account calculator
Estimate January and July tax payments, including your balancing bill and payments on account. See first-year and existing-payer examples.
Enter your figures
Estimated amount due by 31 January 2027
Inputs changed. Select Calculate result to update your estimate.
Enter the relevant liability after tax deducted at source, but before subtracting earlier payments on account. Put Capital Gains Tax, student loan repayments and any applicable Class 2 NI in Other bill amounts. The exemption answer must be confirmed; exactly 80% is not more than 80%. Assumes no approved reduction, late interest, penalties, other outstanding debts or refunded credits. Check your HMRC statement for the actual allocation and due dates. This tool schedules an existing bill; it does not calculate the tax liability.
Why a January tax payment can exceed your annual bill
Payments on account are advances towards a later tax bill. This calculator separates those advances from the balance still owed for the tax year you have just completed, so you can plan the cash needed at each deadline.
Find the figures on your Self Assessment calculation
Enter the relevant Income Tax and Class 4 National Insurance after deductions at source, before taking off earlier payments on account. Add other amounts, such as Capital Gains Tax or student loan repayments, in the separate field. Those amounts may be due with the balancing payment but are not included in this model’s advance-payment base.
The earlier payments field is only for payments already made towards this specific bill. Do not put a future payment here. Confirm the more-than-80% exception from your circumstances or HMRC statement rather than guessing from one payslip.
A first-year example
With a £3,000 relevant bill, no excluded amounts and no earlier advances, the example produces £4,500 for January and £1,500 for July when payments on account apply. January includes the £3,000 bill and the first £1,500 advance; this is cash timing, not a £6,000 tax charge for one year.
Use the result alongside your HMRC statement
Credit is assumed to remain on the account and offset the amounts shown. Refunds, other debts and an approved reduction can change the payment schedule. This calculator does not submit a request to reduce payments or update your HMRC account.
How the self assessment payments on account calculator works
If relevant liability is at least £1,000 and the more-than-80%-paid-outside-Self-Assessment exception does not apply, each new payment on account is half the relevant liability. January combines the balancing bill with the first advance; July contains the second advance. Retained overpayment credit is applied to January, then July.
UK data and rules
2026/27 data · Checked 17 October 2026. Rules are a dated snapshot, not a live feed.
Read about data coverage and updates
Worked example: self assessment payments on account
This illustration uses the calculator’s example inputs. It is not a quote or a recommended financial decision.
- Relevant tax and Class 4 NI after source deductions (£)
- 3,000
- Other bill amounts excluded from payments on account (£)
- 0
- Payments on account already paid towards this bill (£)
- 0
- Tax year of the bill
- 2025/26 — January and July 2027
- Was more than 80% of tax paid outside Self Assessment?
- No — including exactly 80%
Estimated amount due by 31 January 2027: £4,500.00
If relevant liability is at least £1,000 and the more-than-80%-paid-outside-Self-Assessment exception does not apply, each new payment on account is half the relevant liability. January combines the balancing bill with the first advance; July contains the second advance. Retained overpayment credit is applied to January, then July.
Self Assessment payments on account: questions answered
Does a bill of exactly £1,000 trigger payments on account?
The under-£1,000 exception does not cover exactly £1,000. This tool includes payments on account at that boundary unless the confirmed more-than-80% exception applies.
Does the calculator work out my tax from profit?
No. Use the sole trader tax calculator for a separate tax estimate, then confirm the relevant bill amount before using this cash-flow scheduler.
What happens if I have already overpaid?
The illustration keeps the credit on the account, applies it to January and then July, and shows any remaining credit. Actual HMRC allocation, refunds or other charges may change that outcome.
Using your result
Example inputs are a starting point. Replace them with your figures and select Calculate result. Results are rounded for display; calculations use unrounded values.
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