North Belfast Sinn Fein MP John Finucane is still working full-time for his law firm.
He revealed in the House of Commons register of members' interests he was doing 40 hours a week for Finucance Toner.
The prominent lawyer does not take his £79,468 MP's salary because he does not take his seat, but he is still eligible for office costs and staff funding.
The register of members' interests indicates that Mr Finucane is paid £4,672 a month by his law firm. Among the 40-year-old's high-profile clients is Belfast boxer Carl Frampton, who is suing former manager Barry McGuigan's Cyclone Promotions (UK) Ltd over an alleged failure to pay purse money from his bouts.
Mr Finucane also declared £1,608.74 paid by Belfast City Council for his role as Lord Mayor of the city.
This ceased on January 7 after his election to Westminster.
Last year Sinn Fein's seven MPs were paid nearly £120,000 in expenses, leading to calls for the rules to be changed. Foyle MP Elisha McCallion, who in the recent general election lost her seat to SDLP leader Colum Eastwood, claimed almost £25,000 - the most of all Sinn Fein's MPs.
West Tyrone's Orfhlaith Begley claimed the least, at just over £12,000.
Mr Finucane was elected the MP for North Belfast in December last year.
He managed to turn the 2,081 majority enjoyed by the DUP's Nigel Dodds into a 1,943 lead for himself.
At the previous election in 2017 he reduced Mr Dodds' majority by nearly 3,000 votes.
Sinn Fein has always maintained that its elected representatives take home the current average industrial wage on both sides of the border.
But there have been instances where its politicians have been shown to be, or admitted to, taking home much more.
In 2018, for example, Dublin North-West TD Dessie Ellis struck a deal with party chiefs to allow him to keep his €93,598 (£82,493) salary.