Almost one million taxpayers missed the Jan 31 annual tax return deadline this year, triggering immediate fines of close to £100m.
In total 958,296 people failed to submit their self-assessment tax returns on time, according to HM Revenue & Customs (HMRC).
A total of 11.1 million did hit the deadline of the end of Friday to complete their self-assessment tax forms. As usual, there was a surge of last minute submissions, as thousands of taxpayers filed their tax returns in the last hour with 26,562 completing their returns from 11pm to 11:59pm on deadline day.
The department will treat those with genuine excuses leniently"
Mostly those with more than one source of income and the self-employed are required to complete returns.
Angela MacDonald, director general for customer services at HM Revenue and Customs (HMRC), said: "Customers who have missed the deadline should contact HMRC.
"The department will treat those with genuine excuses leniently, as it focuses penalties on those who persistently fail to complete their tax returns and deliberate tax evaders. The excuse must be genuine and HMRC may ask for evidence."
Previous, failed, excuses for missing the deadline in recent years had included someone claiming they were unable to log on because they were up a mountain in Wales.
Late returns attract an initial £100 penalty, which applies even if there is no tax to pay or if the tax due is paid on time. After three months, there are additional daily penalties of £10 a day, up to a maximum of £900.
After six months, there is a further penalty of 5% of the tax due or £300, whichever is greater. After 12 months, another 5% or £300 charge applies, whichever is greater. There are also additional penalties for paying late of 5% of the tax unpaid at 30 days, six months and 12 months.
HMRC is urging anyone who missed the deadline to contact the tax office.