TAX experts are calling for an investigation into why a "growing" number of people are failing to cope with the Inland Revenue's self

assessment system.

With more than three million returns still outstanding nationally - around 104,000 in Kent - accountants fear the January 31 deadline will be

missed by more taxpayers than ever before, resulting in a record multi-million pound windfall in fines and surcharges for the Treasury.

In the last three years, self-assessment penalties collected by the Inland Revenue have increased five-fold to more than £50million.

Linda Wiggins, Maidstone-based president of the South Eastern Society of Chartered Accountants, said a study was needed to determine what was going wrong.

"We are now in the fifth year of self-assessment, but the number of people who send in returns late, or not at all, is increasing and we need to know why," she said.

"The system is very complex, which may be the reason many just don't or can't do it properly, but it's in everybody's interests that some attention is given to what's going wrong."

Taxpayers who do not use a professional adviser will now have to work out how much they owe, but Mrs. Wiggins said they could easily be baffled by the Tax Calculation guide, amounting to between 15 and 32 pages.

Around a quarter of a million people in Kent - mainly high earners and those who receive untaxed income - are required to submit self-assessment returns.

Those who miss the January 31 deadline will incur an automatic fine of £100, and may have to pay interest on outstanding tax at the rate of 6.5 per cent until the debt is settled.

An Inland Revenue spokeswoman denied that the problem was getting worse. "It compares very favourably with last year," she said. "There is no cause for concern."

She said that the number of people filing by the Internet had risen by 72 per cent, but the total number - in early January - is still only around 53,000, a small proportion of the nine million returns sent out.

The Inland Revenue was always seeking ways of improving the system and would welcome suggestions from the Society.

Meanwhile, the Maidstone Tax office is remaining open until 8pm on January 29, 30 and 31.

The Inland Revenue has introduced a system of 'cold calling' by telephoning some taxpayers to remind them of the deadline.

The groups most likely to receive calls are those who filed late returns in previous years, people new to the system, and taxpayers in the Construction Industry Scheme.