A glitch in HM Revenue and Customs' online self-assessment tax return system yesterday meant many taxpayers' accounts were not visible on the system.

The problem followed routine maintenance work on Tuesday.

'We are sorry that some of our agent customers experienced some problems with our IT systems yesterday. We made an enhancement to our systems on Tuesday night and this led to some agents experiencing problems with the client listing service,' said a spokesman for HMRC.

Systems were only affected for a few hours, and the service has returned to normal today without any adverse affects.

HMRC apologized to users of the system but said that slight glitches were inevitable in the performance of necessary upgrade work.