MP and MLA constituency offices are ineligible for the Small Business Grant Scheme set up by the Stormont Executive.
However, under the scheme, launched in March, a £10,000 (€11,000) payment was automatically sent to any firm in receipt of small business rates relief.
Sinn Féin said the money has since been paid back.
“Three Sinn Féin offices received automatic and unsolicited payments of £10,000 under the Small Business Grant Scheme,” a spokesman said.
“Sinn Féin offices did not qualify and did not apply for the scheme and the monies have been returned to the LPS (Land & Property Services).”
The payments were reported on BBC Radio Ulster’s Stephen Nolan Show on Wednesday.
The report said that West Tyrone MLA Maoliosa McHugh’s office was one of the three Sinn Féin accounts which received the payment.
Mr McHugh told the programme 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.
TUV leader Jim Allister has queried how much time elapsed before the money was paid back.
He said he has asked the Commissioner for Standards to investigate.
— Jim Allister (@JimAllister) October 28, 2020
Earlier this week it emerged that 52 wind turbine owners were also among those who received the payment.
The Department for the Economy, which runs the scheme, has since ruled that sector ineligible for grants.
The department defended its actions amid the “scale of the challenge” presented by the pandemic.
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“The department has paid out more than £338 million to more than 32,000 businesses across the £10,000 Small Business Support Grant, the £25,000 Retail, Hospitality, Tourism and Leisure Grant, and the NI Microbusiness Hardship Fund,” a spokesman said.
“It should be noted that the scale of the challenge presented by the pandemic, and the unprecedented speed and scale of the Executive’s response to it, was acknowledged by Comptroller and Auditor General Kieran Donnelly in the NI Audit Office report of 2 September 2020 on the Executive’s response to the Covid-19 pandemic.
“The department will, where possible, seek to recover any funding that may have been paid to those deemed ineligible to receive payment.”