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HMRC internal manual

Self Assessment: the legal framework

HM Revenue & Customs
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Self Assessment Tax Returns: information to be included in the Tax Return

Specification of information required in a self assessment tax return

Section 8(1)

The information required in Self Assessment tax returns is such information ‘as may reasonably be required’ to establish the amounts in which a person is chargeable to income tax and capital gains tax. It includes information needed by HMRC to check that the self assessment is correct. For example it will include all the information needed to calculate the tax due on the taxpayer’s total income and any chargeable gains, for the period covered by the tax return. This will be true whether the calculation is made by the taxpayer or by HMRC.

Use of provisional figures in tax returns

There are occasions on which some information cannot be finalised within the formal self assessment time limits despite the taxpayer’s best efforts to do so. In such cases the taxpayer should include a ‘best estimate’ of the information in the tax return and, if appropriate, a corresponding provisional figure of the tax due. The provisional figures should be clearly identified as such in the tax return. A tax return containing a provisional figure should only be submitted once it is clear that a more accurate figure will not be available before the filing date.

It helps HMRC to have a reason for the use of a provisional figure put on the tax return together with an approximate time when the final figure is likely to be available.

A tax return containing a provisional figure will not be regarded as unsatisfactory, but HMRC will consider whether to open an enquiry to look further at any provisional figure. A penalty for a careless or deliberate inaccuracy in a tax return could be charged if HMRC find there was no good reason for using a provisional figure or the amount was not estimated reasonably.

Once the correct figure is available it should be notified to HMRC without delay, together with any amended self assessment. If there is unreasonable delay in submitting the correct information, and there is additional tax to pay, HMRC would be able to charge a penalty on the basis that the original estimate was insufficient even if the inaccuracy was neither careless nor deliberate when the original tax return was submitted.

Use of judgmental figures, for example valuations, in tax returns

Valuations necessarily require the exercise of judgement, and more than one figure may be equally sustainable. Where necessary taxpayers should enter valuations in their tax return, indicating how they have been reached. If the figure is provisional it will be treated as in Use of provisional figures in tax returns above, but if it is considered final, it will be regarded as the final figure subject to HMRC’s right to enquire into the tax return (see SALF400) and the taxpayer’s right to amend the return (Corrections of errors or omissions in the tax return in SALF204) or to make a claim to overpayment relief (Error or mistake relief claims in SALF206).

Informal advice and uncertainty

Taxpayers who need guidance on completing any part of a tax return can seek help from their HMRC Enquiry Centre or local HMRC office, from the website at or, in the evenings and at weekends, from the Helpline on 0845 9000 444.

However, there may still be some occasions when the taxpayer is uncertain as to the accuracy or completeness of some part of the tax return. In any such case the taxpayer should complete the tax return on the basis that appears most appropriate and should include full details of the points on which they are uncertain in the return. If they do this and the tax return is checked at a later stage, they will not be penalised if they were wrong, provided their original view was reasonable and they had disclosed all the relevant facts.

HMRC rulings

HMRC Code of Practice 10 ‘Information and advice’ describes post-transaction rulings, when and how to ask for one and the extent to which HMRC are bound by a post-transaction ruling. A post-transaction ruling is a ruling given by HMRC on the application of tax law to a specific transaction after that transaction has taken place. Taxpayers can seek binding rulings on completed transactions from HMRC before completing their tax returns. The return can then be completed on the basis of the treatment set out in the ruling.

Inaccuracies in the tax return

Taxpayers must take reasonable care to complete tax returns correctly. Innocent mistakes will not be penalised. Provided the tax return is sent in on time the taxpayer has at least a year to amend it (see Corrections of errors or omissions in the tax return in SALF204).

Of course, inaccuracies brought about carelessly or deliberately are subject to penalties. In calculating the amount of any penalty HMRC take into account the extent to which the taxpayer was helpful in putting things right and volunteered information freely and fully.

Overpayment relief claims

Section 33 and Schedule 1AB

In addition to the right to amend the self assessment within 12 months of the filing date (Corrections of errors or omissions in the tax return in SALF204) the taxpayer is entitled to make a claim for overpayment relief not later than four years after the end of the tax year concerned.

Schedule 1AB paragraph 2

However, no claim is possible if the claim is in respect of:

  • a mistake concerning the basis on which the returned tax liability was calculated, and that basis was the generally prevailing practice at the time the tax return was made, or
  • an error or mistake in a claim that was included in the tax return. (There are separate procedures for making such claims - see SALF600).

So a taxpayer cannot claim overpayment relief simply because HMRC announce that they have changed their practice in relation to the treatment of some particular item.