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Top Tips for last minute returns

A summary of top tips for dealing with last minute tax returns; what not to forget, and how to protect against enquiries.


The normal filing deadline is 31 October 2018 for paper returns and 31 January 2019 for online filing.

If a return cannot be filed electronically if it is covered by one of the 60 odd online filing exclusions. These are cases where HMRC has been unable to provide a correct specification for software suppliers. In most cases, paper returns should instead be filed, by 31 January, together with a reasonable excuse claim.

A later filing deadline may be given when HMRC have received notification of chargeability and were unable to provide a notice to file within the normal deadline.

If underpayments are to be included in the taxpayers' code for the following year, their return needs to be filed by 30 December 2018.

Who must file a return?

  • Anyone who has received a notice to file a Self Assessment return.
  • Anyone with taxable income or gains should have notified HMRC of chargeability. HMRC will then issue a notice to file.

Voluntary Tax returns

  • Backdated, as from April 1996, Income tax, Capital Gains Tax and Corporation Tax voluntary tax returns are to be put on a statutory basis, making them legally valid returns.

Directors tax returns

  • HMRC have updated their guidance about when a director has to file a tax return.
  • The guidance now states that where all of a director’s income is taxed at source and there is no further tax to pay, they do not have to register for and file a Self Assessment return.
  • See Do I need to file a tax return?

The taxpayer must register with HMRC in order to obtain a Unique Taxpayer Reference (UTR)

  • Online filing of a tax return is not possible without a UTR.
  • Apply as early as possible as it can take up to 10 working days from registration for the UTR to arrive.

If the taxpayer does not have a PAYE reference for their employer

  • The current guidance is to use 'None' to enable the return to be filed.

Use of estimates: do not forget to tick the box

  • It may be OK to use estimates provided that you tell HMRC that you have done so by ticking the estimates box.
  • You also need to provide an explanation as to why you have used estimates in order to avoid later penalties or discovery assessments.
  • There is a high risk of penalties for deliberate error if you fail to provide actual figures, you make a delay in providing figures or if it transpires that you simply ticked estimates because you were too disorganised to file a tax return on time. 
  • In short, to avoid penalties, if you use an estimate you need to ensure that you have a reasonable excuse for not providing the correct figures in time.

Using the 'white space' in the return

  • The main SA100 return and additional pages (capital gains, employment etc) all have 'white space' boxes to allow for more details to be provided to HMRC. 
  • These can be used for areas of doubt to ensure HMRC have full details to protect against discovery assessments; careful consideration should be given to what is included here as it is classed as being part of the tax return and penalties can result for inaccuracy in the same way as if boxes of the return have incorrect figures in them.
  • See How to appeal a tax penalty and Discovery assessments and time limits.

The remittance basis and deemed domicile

  • The remittance basis is no longer available for those who are deemed UK domiciled at 6 April 2017.
  • All income and gains must be included on the return whether remitted or not.
  • See Non-domicile status, deemed domicile and tax

Use of home adjustments

If you are self-employed and work from home:

  • You can claim all the costs that are incurred for business purposes.
  • You may also claim a proportion of all the other costs of running your home, such as light and heat, insurance, council tax, repairs, cleaning and mortgage interest.
  • There is no set method of apportioning these other costs; it depends on what work is carried on at home.
  • From 6 April 2014, a taxpayer may claim a monthly fixed rate allowance for home working instead of making a claim for their actual expenditure: this is a low figure and so actual expenditure may yield higher tax relief.
  • See Use of home as office calculator

Private use adjustments

  • The self-employed must make adjustments for private use of vehicles and property where relevant.
  • If your vehicle is used partly for private purposes you need to make a tax adjustment to disallow a proportion of your running costs that relate to that private use.
  • If you disallow a proportion of running costs, you must adjust your claims for capital allowances too.
  • Assets that have mixed-use must be pooled separately from other assets.


  • Beware the annual allowance taper for high earners and those with large pension pots such as NHS doctors; fund growth goes towards the £40,000 limit and can result in tax charges. See our Pensions guide for more details.


  • Don't forget to take account of losses brought forward, especially capital losses which can be overlooked as not relevant until a capital gain occurs.
  • Remember the Sideways loss relief cap of £50,000 or 25% of adjusted net income for sole traders wishing to offset trading losses against other income.
  • Losses in the first four years of trading can be carried back three years and terminal losses go back three years.
  • See our guide Losses, trade losses and sideways relief.

Higher-income benefit charge

  • Don’t forget to complete this section if:
    • Income is over £50,000.
    • Child benefit has been received by the taxpayer or their spouse or partner.

Trading and property allowance

  • If income from trading or property is below £1,000 check if the new trading and property allowances apply.
  • If so you do not need to complete the self-employment pages and/or Property pages of the return as appropriate.

Restriction of relief for residential financing costs

  • For 2017/18 75% of finance costs are deductible from rental income and the remaining 25% (or the remaining profits whichever is lower) are allowed at 20% only.
  • This applies to all financing costs and not just mortgage interest.
  • See Forms tab for how to input on the tax return.

Finally don't forget to follow up. Items spotted during the tax return process can result in amendments being required to previous years' Self Assessment returns or to previous VAT or PAYE returns, as well a requirement for voluntary disclosures to be made to HMRC. 


Client guide to reasonable care and tax penalties

Penalties: errors in returns and documents