The IR says 'well-established arrangements' ensure correct tax

The details of several million people are said to be missing from the second system.

The Inland Revenue admits there are problems in sending information from one system to the other but says the details can be recovered and the process has already started.

In a statement it said: "The Inland Revenue has well established arrangements to deal with these situations and ensure that the correct information is obtained and the right amount of tax is paid."

It is vital for the Inland Revenue that the details are successfully stored in the correct system to ensure that employers have deducted the right amount of tax from their employees' pay.

The ACCA says the tax service should offer some form of compensation to those affected, in the same way that taxpayers must pay a 5% surcharge for late returns.

It says the IT problem could lead to some taxpayers having to wait for a tax rebate, or they may receive the wrong amount.

Chas Roy-Chowdury, head of taxation at ACCA, told BBC News Online: "Every year the Inland Revenue has a problems with its IT system and the processing of self-assessment forms."

"It never offers taxpayers any slack when they fail to get their tax returns in on time, so in this case it should certainly offer those affected a gesture of goodwill," he said.