Despite the record, an estimated 600,000 customers missed the deadline and now face the risk of penalties.

Some 12,060,872 Self Assessment returns were due with 11,733,465 (97.3%) of returns received by 31 January.

The penalties for anyone who has missed the 31 January deadline start at an initial £100 fixed penalty. This applies even if there is no tax to pay or if the tax due is paid on time.

After 3 months there are additional daily penalties of £10 per day, up to a maximum of £900. After 6 months there is further penalty of 5% of the tax due or £300, whichever is greater.

HMRC said 10.9m returns were filed online and 385,296 paper tax returns were filed (3.4% of returns expected). Data is not yet available on how the remainder were filed.

There were 36,767 customers who filed in the last hour before the deadline, but the peak hour for filing on the day was 4pm and 4.59pm, when 68,462 customers submitted their tax return.

Despite the threat of penalties, HMRC has urged anyone who has been late in filing their returns to get in touch straightaway.

Myrtle Lloyd, HMRC’s director general for customer services, said: “Customers who have yet to file, and who are concerned that they will not be able to pay in full, may be able to spread the cost of what they owe with a payment plan.”

HMRC has again warned customers to be wary of scams and said they should never share their HMRC login details with anyone, including a tax agent, if they have one. HMRC scams advice is available on GOV.UK.  HMRC is one of the organisations most targeted by scammers in the UK.