According to HMRC more than 870,000 taxpayers missed the 2016 deadline and paid, at least, the £100 fine. There is talk from HMRC about changing the severity of this flat £100 fine in the near future, but it will still be in place for 2015/16 returns, so don't be late. If you are one of those last minute submitter's, here is a useful check list and some tips that we at Listentotaxman have come across.

• Get your return in ASAP! You are not the only one leaving this until the last minute, in fact, in 2016 over 50,000 people completed their online return on the 31st, the busiest times being between 4pm and 5pm, so expect the system and helplines to be very busy. 
• Understand the tax dates. The 31st Jan 2017 deadline is for the self-employed income that you earned between 6 April 2015 and 5 April 2016. Any expenses you are claiming back, are to be from that time period also. 
• If you do not have exact figures for required totals such as interest earned on your savings, put in reasonable estimates for now. You can tell HMRC in the additional information box on your return that the figure is an estimate and go back in as soon as possible with an accurate figure. Do make sure to use as accurate an estimate as possible.
• If you are missing documents such as your P60, bank interest certificate, etc., use your most recent statements and wage slips to get the relevant information. In most cases these will be dated from March. If you can not find March's wage slips, statements etc., use the telephone to contact your bank, employer, fund managers and so on to get the information.
• Don't forget to include interest on savings and dividends (whether cash or reinvested) on your return.
• Make sure to check your previous Self Assessment returns for losses that can be offset against any gains/ income  this year. HMRC will not do this for you. In order to receive any tax relief owed you must carry the loses forward yourself. HMRC have information on claiming losses against income for self employed.
• Do not round up your figures. HMRC have implied that rounding up figures is a sign that people have not been detailed in maintaining their accounts and could attract further attention from HMRC.
• Take the time to go through your expenses, both personal (eg. pension contributions, charitable donations, etc.) and business. Claiming for your allowable expenses is the surest way to reduce your tax bill. Check out our article on allowable business expenses for PAYE Employees and the Self Employed. HMRC have information on allowable business expenses for those self employed. 
  
• If you have gone over your allowable pension contribution you may be able to carry forward unused allowances from previous years, see more.
• Make sure to complete a separate supplementary page for each individual employment, if you have more than one.
• Use the right figures, ie. do not enter a net figure where a gross is required, or vice versa.
• Double, no, triple check that you have completed all relevant sections, as this common mistake is one of the main reasons HMRC will reject a return. Also make sure that any necessary supplementary pages of the return are completed.
• Consider if Capital Gains applies to you this year, eg. have you sold a property? Or have you incurred a loss? If so you need to fill out the relevant section.
• Remember that the 31st January deadline is for the payment of taxes owing as well as the return of the form.  You need to pay any tax owing, and complete your return on time, to avoid fines. However, if for some reason, you cannot pay the tax by the 31st January, at least make the return as the fines for not making the return on time can be very costly, even if no tax is owing.
• If you are self employed and your profit is less than the personal allowance (£10,600 in 2015/16) don’t use your Annual Investment Allowance for assets purchased, as you will not be liable for tax. Carry forward the value and write off in future years when you have tax to pay. HMRC has details on the Annual Investment Allowance.
• If you are not sure about something you have included, for example whether a cost is allowable or not, explain your concerns to HMRC and the reason why you have included it in the additional information box on the return.

For more information on making your return, see :

 Self Assessment Guide.

Business expenses you can claim back as a PAYE Employee

Business expenses you can claim back as Self Employed

Working from home allowance

The Cost of a Late Return: breakdown of fines and penalties

HMRC have a written guide on completing your return here.