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HMRC internal manual

Self Assessment Manual

Amend payment: claim to adjust payments on account: rules for calculating payments on account

The rules below describe the statutory basis for calculating payments on account (PoA).

Calculation of payments on account

The calculated PoA are half the previous year’s Tax and NIC liability after the deduction of any

  • Capital Gains Tax
  • Tax deducted at source
  • Underpayment transferred to COP
  • SA student loan repayments

Payments on Account are calculated and created automatically when

  • The return is captured for the preceding year unless the record is dormant, see section ‘Maintain Taxpayer Record’ SAM101000 onwards’, or
  • A Determination, Revenue amendment (SAM21020) or Jeopardy amendment (SAM21010) is made for the preceding year

Manual procedures exist for creating PoA when an SA year is included in a contract settlement (SAM31060) or where a discovery assessment is raised. For more information see business areas ‘Compliance’ (SAM31000) and ‘Assessments’ (SAM20000 and SAM21000) respectively.


1. The calculated PoA are the most a taxpayer can be expected to pay on account of the final liability for the tax year. There are some exceptions (SAM1010) where PoA are not required.
2. The tax and NIC split is not identified on the taxpayer record and is not required for the purposes of collecting payments on account.
3. Payments on account are not set up where the Last SA Return Required for Year Ending 5th April field is set to the previous year or all the liability for the previous year is coded out.
4. Any amounts held over, either formally or informally, are ignored and only the collectible amount(s) are used to calculate the payments on account.
5. Any odd 1p is loaded on the second PoA.