When IT fails, you can guarantee it will happen at the worst possible time.

For the Inland Revenue, that moment was last Tuesday. Right in the middle of the busiest month of the year. Over 9.5 million UK taxpayers need to file self-assessment tax returns by the 31st of January. Last year, over a million filed using the Revenues online filing website.

The online functionality was only available intermittently between 3pm and 10pm. The cause was a server failure.