The deadline for filing your self-assessment tax deadline is tomorrow and risk a fine from HMRC if you miss it. This year's deadline is for the 2023-24 tax year, and HMRC warns that if you fail to submit on time, you could face an initial late filing penalty of £100. This applies even if there is no tax to pay or if the tax due is paid on time. After three months, additional daily penalties of £10 per day are added, up to a maximum of £900.

After six months, a further penalty of 5% of the tax due or £300 is then added - whichever is greater. After 12 months, another 5% or £300 charge is added. There are also additional penalties for paying late of 5% of the tax unpaid at 30 days, six months and 12 months. If the tax remains unpaid after the deadline, interest of 7.25% is also be charged on the amount owed, in addition to the penalties.

Most UK taxpayers have their taxes deducted automatically from their wages, pensions or savings, and won't need to file a tax return. But tax returns are due from individuals or businesses that haven't had tax automatically deducted, or that have earned extra untaxed income. According to research from Handelsbanken Wealth & Asset Management, more than 300,000 people could miss the January tax deadline. This research comes alongside data from HMRC, which revealed that, as of January 23, around 5.4 million people had yet to file their returns for the 2023-24 tax year.

The research revealed that worries and concerns about self-assessment are on the rise among the self-employed with 17% saying they were worried about the financial consequences of making a mistake when filing. This is compared to 11% in the same survey conducted last January. A further 16% expressed concerns about the financial repercussions of missing the deadline - only 11% said the same last year.

Around 11% say completing self-assessment returns is challenging because of their lack of financial knowledge, and 12% say it is tough due to the complexity of calculating their income. A further 9% stated that they find self-assessment forms challenging due to their poor record-keeping throughout the year. Mark Collins, Head of Tax at Handelsbanken Wealth & Asset Management said: “Self-assessment returns remain challenging for substantial numbers of the self-employed, with many at risk of missing the January 31st deadline and others lacking confidence when completing forms. Customers filing their returns late risk a £100 fine, even if there is no tax to pay. Penalties can mount up if returns are more than three months late, with additional penalties for paying outstanding tax late.”.

You normally need to file a self-assessment tax return if you're self-employed and your income hasn't had tax automatically deducted, or if you've earned extra cash outside of your normal employment that has not been taxed. You can also check online through the HMRC website to see if you need to send a tax return. Get our money-saving tips and top offers direct to your inbox with the Mirror Money newsletter.