The money incorrectly paid to a Sinn Féin senator and her husband in late March was only paid back on Tuesday this week, the Irish Examiner can reveal.
Derry Senator Elisha McCallion and two others have resigned from the party after failing to return money paid to them in error.
It emerged this week that three party offices incorrectly received money under the Northern Ireland Executive's Small Business Grant scheme.
Under the scheme, launched in March, a £10,000 payment was automatically sent to any firm in receipt of small business rates relief.
It's understood there have been around 450 errors out of 27,000 grants paid out. 70 of those have had the money recovered while the processing the other errors is ongoing.
The rates reliefs scheme had been open to small political offices but MP and MLA constituency offices are ineligible for the Small Business Grant Scheme.
It appears that in the last financial year Ms McCallion's former constituency office would still have been on the Land and Property Services list and was given the grant in error.
The grants were first paid out in March, Sinn Féin's investigation into the incident started on Monday evening, sources confirmed.
Multiple Sinn Féin sources have confirmed that Ms McCallion was told "in no uncertain terms she had to go," and was informed that she was "finished" in the party, despite Ms McDonald's statement saying the former Foyle MP had resigned.
President Mary Lou McDonald released a statement on Thursday which said: "On Monday and Tuesday, the Sinn Féin leadership established that three party offices incorrectly received lodgements of £10,000 under the Small Business Grant scheme established by the Department of Economy in March 2020.
"Last night I accepted the resignations of the three individuals responsible for these accounts and for not returning the money - Senator Elisha McCallion, the Chair of Upper Bann Comhairle Ceantair, and a party official in West Tyrone.
"The failure to immediately return grants erroneously paid into Sinn Féin accounts is a most serious situation. As party leader, I wish to acknowledge and apologise for these failures.'
"The payments were not applied for and were automatically received.
“Payments were paid into constituency accounts in West Tyrone and Lurgan, and into Elisha McCallion’s account in respect of her former Westminster office.
“In each case the grant money has been returned in full, with repayments made on Monday and Tuesday of this week.
“These monies should have been returned immediately as no political offices qualified for this grant.
“The party has established in each case where responsibility lay for the administration of the accounts in question and for the reimbursement of these monies.
“The Sinn Féin Ard Chomhairle met last night and censured all those involved.
“Last night I accepted the resignation of Senator Elisha McCallion. She accepts full responsibility for the failure to return the grant immediately.
“The party also accepted the resignation of the party official in West Tyrone who had responsibility for the administration of the account and failed to promptly return the grant money despite being requested to do so by Maolíosa McHugh MLA.
“The Cathaoirleach (Chairperson) of the Upper Bann Comhairle Ceantair (Constituency Organisation) has also tendered his resignation in recognition of their failure to return the grant payment in a timely fashion.
“The Small Business Grant scheme was established to support struggling businesses in times of extraordinary hardship.
“The failure to immediately return grants erroneously paid into Sinn Féin accounts is a most serious situation.
“As party leader I wish to acknowledge and apologise for these failures.”
Ms McCallion also released a statement saying: "Earlier this year a Small Business Grant was lodged into a joint account of which I am a named signature with my husband.
"I did not apply for nor solicit this money nor did I receive any correspondence from the department in relation to it.
"I fully accept that as a named signature on the account that I should have taken extra steps to verify this situation, before it was brought to my attention on Tuesday.
"The money was repaid in full on Tuesday.
"I apologise unreservedly for the poor judgement I showed in relation to this and therefore, last night I spoke to the party leader and tendered my resignation as a member of Seanad Éireann with immediate effect."
Mr McHugh said on the BBC yesterday that he had contacted party officials to make arrangements to pay the money back “quite a while ago”, adding that he received confirmation earlier this week that it had been repaid.
Staff in Sinn Féin say they are in shock at the development, with one source telling the Irish Examiner: "I don't know what they were thinking."
Sources in Ms McCallion's Comhairle Ceantair in Derry city say they knew nothing of her departure until contacted by the Irish Examiner, and had not been contacted by the party headquarters.