The Revenue admitted its entire system had collapsed for 90 minutes on Monday. Accountancy Age has also received reports of breakdowns occurring last week.
Accountants said the problems meant tax offices were unable to answer queries about taxpayers, leading to serious delays in getting agreed payment slips to clients in time.
The computer problems aggravated the existing confusion caused by 800,000 incorrect tax demands that were inadvertently sent out by the Revenue three weeks ago.
As a result, some firms are calling for an extension to the time limit before interest starts to run on late payments.
Shortcomings in the system will be highlighted when Revenue officials appear before a committee of MPs next week.
The Treasury sub-committee will review the Revenue’s progress in introducing self-assessment, both for individuals and companies.
Committee chairman Sir Michael Spicer MP said: ‘There are clearly areas of concern that have been flagged up, such as computerisation.’ The committee will also assess the Revenue’s progress in encouraging compliance, particularly within small businesses.
It will also consider the impact on the Revenue’s staff and technology resources of its merger with the Contributions Agency. Concerns have also been growing over a shortage of experienced tax inspectors.
The Revenue said last month it would contribute to a rolling programme of improvements in the system.
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