Consumers could be fined more than £440 million this year for handing in their self-assessment tax forms late or miscalculating how much they owe, it was estimated today.
Professional advice website Unbiased.co.uk claims people will hand over £442 million 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 £116 million for failing to submit their form by the January 31 deadline, while they will have to pay £310 million in charges for miscalculating how much tax they owe.
People are also expected to have to hand over a further £16 million in surcharges for unpaid tax from previous years.
Overall, the group expects people to be fined around £12 million 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% 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.
Karen Barrett, chief executive of Unbiased.co.uk, said: "Taxpayers around the UK face hefty fines if they fail to fill out their self-assessment forms correctly and in time for the January 31 deadline.
"Last year over one million forms were filed late, leading to penalties and in most cases additional surcharges.
"In this tough economic climate, where money is tighter than ever, we are urging consumers to take 'tax action' and plan carefully."