Paul Gray, who quit as HM Revenue and Customs boss over lost data discs, is back working for the government.
Mr Gray was praised for resigning "as a matter of honour"
He was praised for resigning with "honour" when discs holding the child benefit database were lost in the post.
Channel 4 News reported that he had begun a short-term Cabinet Office post and is still paid more than £200,000.
But a government spokesman said Mr Gray's period of notice meant he would continue to be paid until 31 December whether he was working or not.
"In the meantime he has agreed to a request from Cabinet Secretary Sir Gus O'Donnell to undertake a short piece of work on cross-government matters until Christmas," the Cabinet Office spokesman said.
'No additional cost'
He added the period of notice meant "he could receive payment for no work or receive payment for doing some work.
"It was thought to be better in the public interest that he did some work. There is no additional cost to the public purse. He will leave the payroll on December 31."
HM Revenue and Customs sent two discs containing the entire child benefit database, unregistered and unencrypted, to the National Audit Office by courier in October - but they did not arrive.
The government has apologised and said there was no evidence the discs had fallen into the wrong hands.
But millions of families have been told to be on alert for fraudsters using their details, stored on the discs, which include bank details, National Insurance numbers and children's names, addresses and dates of birth.
Last week Chancellor Alistair Darling said an interim report into what had gone wrong was due within three weeks - and pledged to report its findings to MPs.
Police are still looking for the discs.