Self-assessment tax deadline still looms for two million
More than two million people face a last-minute rush to complete self-assessment tax forms before a deadline.
Some 11.8 million people, primarily those with more than one source of income and the self-employed, are required to complete returns.
Most have met the online filing cut-off at the end of Wednesday, following an earlier deadline for paper returns.
Fines can be issued immediately for late filing, despite plans to shift to a points-based system in the future.
HM Revenue and Customs (HMRC) said that it had received 9.2 million returns, according to the latest available data. Nine out of 10 completed returns had been filed online.
A total of 167,337 people submitted their details on Sunday, the final non-working day before the deadline.
Many have to settle an income tax or capital gains tax bill at the time of the deadline.
Some campaigners have alerted taxpayers to the fact that it is no longer possible to pay tax by credit card or via the Post Office.
Meanwhile, accountants have also expressed concerns that some people may believe the system of fines had already changed.
The current system means HMRC could demand a penalty of £100 for late filling during the first three months after the deadline.
After three months, additional penalties of £10 per day can be demanded, up to a maximum of £900, followed by further charges six and 12 months after the deadline.
However, the government is working on plans to introduce a points-based system, similar to driving offences, for those who fail to submit their tax returns on time, rather than an automatic fine.
This could begin with VAT in the 2019 tax year, before income tax is added to the system later, but some accountants are concerned that people may mistakenly believe such a change had already come into force.
Chas Roy-Chowdhury, head of taxation at the ACCA accountancy body, said now was the time for those needing to complete their self-assessment and pay tax to "get their skates on".