Sinn Féin's Mid-Ulster MP Martin McGuinness is giving back £3,000 (€3,255) in expenses for two months rent for his London accommodation.
In a statement the party said the error had not been picked up on at the time by the Commons Fees Office or by Sinn Féin. The party's four other MPs have not been asked to make any repayments.
Hundreds of Westminster MPs have been asked to repay or justify some of their allowance claims following a review by an independent auditor.
Many are angry that they are being asked to repay claims for services like gardening and cleaning, saying they were within the rules when the claims were made, and approved.
However, Sir Thomas Legg has applied his own annual limits of what he thinks was reasonable to claim. He set these at £1,000 a year for gardening and £2,000 a year for cleaning.
He has also asked those who claimed more to repay the difference. He has also asked for paperwork to back up mortgage interest and rental agreements. In a note to MPs, he warned that those who fail to do so will be 'recommended to repay the whole of the allowance granted for the mortgage etc'.
In Northern Ireland constituencies, seven of the DUP's nine MPs have been asked to pay back a total of more than £14,000 in expenses following a reassessment of their claims. East Antrim MP Sammy Wilson and North Belfast MP Nigel Dodds were not required to repay any money.
William McCrea is to repay £5,329, the highest amount requested.
The South Antrim MP said the repayment related to furniture he purchased, duplicated service charges and a duplicated allowance for a TV licence.
East Derry representative Gregory Campbell has been asked to repay £2,656. He said this related to four items, including accommodation expenses which exceeded the maximum claim allowed, a service change which was overpaid, and two overpayments of ground rent.
Mr Campbell said he was sorry the claim forms had not been checked more meticulously (before submission) and they would have to make sure it did not happen again.
Iris Robinson, wife of party leader Peter, was told to repay £2,274.
Mrs Robinson said her repayment request related to three items, all of which she said she was questioning.
'One relates to the only item of furniture where I believe Sir Thomas has not properly applied the guidelines, one is the identical issue in respect of Peter Robinson (mortgage interest) and the remaining item was for a service charge which was duplicated, but which we believed the amount paid simply reduced a subsequent bill.', she said.
Lagan Valley MP Jeffrey Donaldson said he had been asked to repay £1,964, in relation to accommodation costs, mobile phone charges and a service charge.
Former party leader Dr Ian Paisley has been asked for £1,181, which he said related to a payment from the Fees Office during dissolution.
Upper Bann representative David Simpson has been asked to return £400 in respect of a claim he made for food and party leader Peter Robinson is to repay £229 in relation to mortgage interest.
Mr Robinson said there would be no equivocation or quibbling over any repayment and that all payments should be made immediately.
UUP MP Lady Sylvia Hermon said she was asked to repay £1,365.
Lady Hermon said she had received a letter about repaying rent on a London flat which had been paid twice in the same month by the Fees Office. She said she would be querying the repayment request.
The SDLP said party leader Mark Durkan was recommended to repay £236 relating to overpayment of council tax in 2006 and his wife's share of a London hotel bill. Mr Durkan said that while some of Sir Thomas's findings seemed petty, close scrutiny of MPs expenses was justified.
South Belfast MP Alasdair McDonnell said he had not been asked to repay any of his claims. It's not yet known whether South Down MP Eddie McGrady has been asked to repay any expenses.
Meanwhile, South Down MP Eddie McGrady said despite disputing some of the amounts calculated he will be making full repayment of schedules outlined in Sir Thomas's letter to him for £6112.
Mr McGrady says he intended to query the disputed amounts with Sir Thomas and his team at a later stage.
Summary so far of expenses to be repaid:-
Eddie McGrady (SDLP) £6112
William McCrea (DUP) £5,329
Martin McGuinness (SF) £3,000
Gregory Campbell (DUP) £2,656
Iris Robinson (DUP) £2,274
Jeffrey Donaldson (DUP) £1,964
Sylvia Hermon (UUP) £1,365
Ian Paisley (DUP) £1,181
David Simpson (DUP) £400
Peter Robinson (DUP) £299
Mark Durkan (SDLP) £236
