Consumers could be fined more than £440m this year for handing in their self-assessment tax forms late or miscalculating how much they owe, it was estimated this week.
Professional advice website Unbiased.co.uk claims people will hand over 442m to the tax man this year in fines for late tax returns and miscalculations and surcharges on unpaid tax from previous years.
The group estimates that people will incur penalties of 116m for failing to submit their form by the January 31 deadline, while they will have to pay 310m in charges for miscalculating how much tax they owe.
People are also expected to have to hand over a further 16m in surcharges for unpaid tax from previous years.
Overall, the group expects people to be fined around 12m more than they were last year, due to a combination of more workers now having to complete a self-assessment tax return and more people making avoidable errors.
People who have to complete a self-assessment tax return for the 2009/2010 tax year have until January 31 to do so online, or they incur a 100 late payment charge. The deadline for paper tax returns was October 31.
If the form has still not been submitted by July 31 they are liable for another 100 penalty.
On top of this, they have to pay interest on any unpaid tax, while persistent offenders could face a penalty of up to 60 a day in certain circumstances.
Every year around 10 per cent of the 9.3 million people who have to fill in a self-assessment tax return miss the deadline.
But not all of these people will incur the 100 penalty, as people are only fined if they owe tax.
Around 3.5 million people are thought to have filed an online return so far, although there is normally a last-minute rush in the final days before the deadline.