Tax return self-assessment: How to see if you have to file and how to avoid a fine for filing late

The tax return deadline is fast approaching. At midnight on Sunday (31 January), self-employed people, those earning more than £100,000 a year and people who have an income higher than £2,500 from UK property or land will need to fill in their self-assessment form.

According to Her Majesty's Revenue and Customs (HMRC), more than 21,000 tax forms were filed in the last hour before the deadline in 2014. The late afternoon also sees a big spike in people filling in their returns, so the self-employed are urged to file the self-assessments on Saturday or Sunday morning because HMRC's website might be encountering technical issues due to the high volume of traffic.

Some people might be confused whether they have to fill in the tax return form. HMRC has set up a test on its website where UK residents can check if they have to self-assess before the deadline.

HMRC also urges tax filers to go straight to its website, without using search engines. The organisation also warns of scammers and phising emails. People can check here if an email sent by HMRC is genuine.

If you expect to miss the deadline, it is best to let HMRC know. Those filing tax returns too late have to pay a fine of £100. An HMRC spokesperson told IBTimes UK that people should not count on being exempt from the deadline.

However, if you do file too late, may be able to avoid a fine if you have a "reasonable excuse". "Whether a person has a reasonable excuse for not submitting on time will depend on their particular circumstances and customers have 30 days to appeal if they believe they have a reasonable excuse on what prevented them filing on time," the spokeswoman said.

Excuses will be assessed by HMRC on a case-by-case basis. The organisation has listed the following reasons as legitimate:

• your partner or another close relative died shortly before the tax return or payment deadline
• you had an unexpected stay in hospital that prevented you from dealing with your tax affairs
• you had a serious or life-threatening illness
• your computer or software failed just before or while you were preparing your online return
• service issues with HM Revenue and Customs (HMRC) online services
• a fire, flood or theft prevented you from completing your tax return
• postal delays that you couldn't have predicted

However, not all excuses are good enough to avoid a fine. HMRC listed these as the worst reasons it received last year from people who missed the self-assessment deadline:

• My tax papers were left in the shed and the rat ate them
• I'm not a paperwork orientated person – I always relied on my sister to complete my returns but we have now fallen out
• My accountant has been ill
• My dog ate my tax return
• I will be abroad on deadline day with no internet access so will be unable to file
• My laptop broke, so did my washing machine
• My niece had moved in – she made the house so untidy I could not find my log in details to complete my return online
• My husband ran over my laptop
• I had an argument with my wife and went to Italy for 5 years
• I had a cold which took a long time to go