HM Revenue & Customs (HMRC) has issued a stern warning to UK taxpayers about looming deadlines for submitting self-assessment tax returns. The final date to file your online tax return for this period is January 31, 2026. Missing this deadline could trigger significant financial penalties.
If you fail to file your return within three months after the deadline, a £100 fine will be imposed. Should the delay extend further, daily penalties of £10 will accumulate for up to 90 days, potentially adding up to £900. Beyond six months, an additional penalty of 5% of the tax due or £300—whichever is greater—will be applied. After twelve months, a second 5% or £300 penalty, whichever is larger, may also be charged.
It’s important to note that penalties must be paid within 30 days of receiving the penalty notice to avoid further consequences.
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Taxpayers can amend their returns within 12 months after the self-assessment deadline if any mistakes were made initially. Corrections can be submitted online or via a new paper return, which may adjust your tax liability or entitle you to a refund.
Lucy Pike, HMRC’s Chief Security Officer, emphasized the risk of scams targeting taxpayers during this busy period. She urged the public to remain vigilant, avoid clicking suspicious links, and never share personal information. Suspicious communications should be reported directly to HMRC.
Those required to file a self-assessment return include individuals receiving Child Benefit payments who are liable for the High Income Child Benefit Charge—applicable if either partner earns over £50,000 annually. To determine if you need to file, HMRC provides an online tool on the GOV.UK website.