The audit follows a series of news reports that raised questions about the propriety of some of the allowances claimed by senators.
Conservative Senator Patrick Brazeau's claims are already being reviewed by a special committee, which has now been directed to review the claims made by Liberal Senator Mac Harb as well.
In addition, the Senate's internal economy committee has asked the Senate administration to conduct an audit to determine whether all senators are properly declaring their primary and secondary residences.
Brazeau, who claims the allowance for a secondary residence in Gatineau, Que., has designated his father's home in Maniwaki, Que., as his primary residence, although neighbours say they rarely see him there.
Harb, a former MP who has lived in the capital for decades, has claimed the allowance for his Ottawa home, while designating a property in Pembroke, Ont., as his primary residence.
Conservative Senator Mike Duffy, also a longtime Ottawa resident, has claimed the allowance for his home in the capital while designating a home in Prince Edward Island as his primary residence.
Also on HuffPost