The official face of HMRC in recent years has attracted media attention for channelling her fees through a personal services company.
The BBC newsreader, who fronts the Self Assessment advertising campaign with the catchphrase "tax doesn't have to be taxing", set up the firm that entitled her to pay corporation tax at the small companies rate of 21% on some of her earnings.
The Telegraph reported that Companies House filings reveal she is sole director and shareholder of Moira Stuart Limited. The accounts show that £22,607 was paid into the company in 2010-11, and after £1,749 of administrative expenses, she paid £4,380 in corporation tax on the profit.
The arrangement is legitimate for freelancers, but HMRC is supposed to take action against people who it judges to be "disguised employees".
HMRC has said Stuart works on specific advertising campaigns for HMRC, but is not employed directly so there is no question of disguised employment.
Foreign secretary William Hague was the first senior cabinet minister to condemn the practice of setting up companies through which to siphon salaries.
Speaking on the Andrew Marr show, Hague said: "I'm not very fond of that sort of behaviour. Sometimes people will have agreed their own arrangements and done it over a long time, and that's their contractual arrangement, so of course they will have their legal rights to that. But, particularly at this time in the nation's history, people should be paying their taxes fully."
Service companies have been popular among senior BBC executives for years, but the scale of their popularity across the public sector is now under growing scrutiny.
Last week it was revealed that up to 25 full-time NHS staff, most on contracts as long as five years, are paid through companies owned by their families.
The Department of Health is investigating the claim and whether the staff will be allowed to go on the payroll.
The issue of whether or not the staff in question should be caught by IR35 is expected to come into play, centring on whether they declared they were caught by IR35 as “disguised employees".
The head of the Student Loans Company (SLC) was also found to have been paid through a company, reportedly allowing him to legally save as much as £40,000 a year in tax.
The Treasury is undertaking a wider review across government departments, which is due to be completed by the end of March.