Fines totalling about £7m are set to be handed out for late tax returns – despite a record number of forms being filed on time.
More than 10 million tax returns were received by the 31 January filing deadline, beating last year's total of 9.61 million, HMRC said.
This is the highest percentage of on-time returns ever recorded.
Yet, about 700,000 people, around 6%, failed to return the information when required to – which amounts to at least £7m in fines overall.
Everyone who missed the deadline faces a £100 penalty.
The penalties go up after three months by £10 per day - up to a maximum of £900 - and after six months by a further 5% of the tax due or £300, whichever is greater.
After 12 months another 5% or £300 charge, whichever is more, is handed out.
{desktop}{/desktop}{mobile}{/mobile}
HMRC announced the record for the number of online returns, set last year when 7.93 million people filed over the internet, was also broken, with 8.48million submitting online. This represents 84.5% of all returns received – a record-breaking percentage.
Last minute filing was in evidence with 21,027 people leaving it until between 11pm and midnight on deadline day – which was the busiest day for online returns with 569,847 received.