An air-conditioning failure forced HM Revenue and Customs (HMRC) to shut down computers, disrupting online services earlier this week.
The cooling failure hit the first day of operation for the new Construction Industry Scheme (CIS), along with online services for claimants of working tax credits and child tax credits.
An HMRC spokesperson confirmed: "On Tuesday [10 April] we did have a temperature control problem at one of our data processing centres. As a safety precaution we had to shut down computers there."
He added: "A number of online services were affected, but it was just one day." Services were now working normally, he said.
The problems were related solely to the air conditioning failure, with no problems caused by people logging onto the CIS system for the first time, he said.
Last month, a similar air conditioning breakdown in Florida forced the US state government to shut down computers at a 1,200-server data centre, hitting a range of public services.
IT departments in the UK were badly hit by soaring temperatures and power failures caused by increased demand last summer, with data centre air conditioning systems failing during the heat wave.