Sen. Mike Duffy is once again charging taxpayers for his costs of living in Ottawa, filing the same kind of residency claims that first triggered the Senate expense scandal.

Senate financial reports show that Duffy claimed $1,691 in living expenses for time spent in the National Capital Region, between March and June 2016.

Duffy returned to Senate duty after his acquittal on 31 charges of breach of trust, fraud and bribery, on April 21.

Duffy told CTV by email that all his recent expense claims have been approved.

"I filed my claims as the Senate rules provide, as was approved by Senate administration, and as Judge Vaillancourt agreed were valid," he wrote, referring to the judge who cleared him in the criminal trial.

At the same time, Duffy is also facing demands from the Senate that that he repay nearly $17,000 in expenses it considers ineligible. Duffy has said through his lawyer that he will not pay and calls the attempt to recover the cash an "attack on the final judgment" in the criminal case.

CTV News has learned that the Senate board of internal economy last week wrote to Duffy advising that his paycheques will be garnisheed by 20 per cent until the full $16,955 is recovered.

It was Duffy's original use of National Capital Region expense claims -- which were intended to defray the costs of spending time in the Ottawa-area for out-of-town senators -- that first drew scrutiny of auditors and, later, the RCMP, when they were revealed in 2012.

Duffy had lived most of his adult life in Ottawa and owned a home in the suburb of Kanata since 2004, yet he was able to claim expenses for time he was in town because he said he was primarily resident in Prince Edward Island, where he owned a cottage.

What exactly constituted a primary residence was litigated in excruciating detail at Duffy's trial, leading to his full acquittal on all charges.

Judge Charles Vaillancourt found that there was no definition of primary residency in Senate rules at the time of the claims and no indication Duffy acted fraudulently in making the NCR claims.

Later, the Crown also elected to drop charges against Sen. Patrick Brazeau and former senator Mac Harb, both accused of fraud related to claims for expenses in the National Capital Region.

The new expense claim suggests that Duffy is now in compliance with revised Senate rules, put in place in 2013, that require senators to produce a driver's licence, provincial health card and Canada Revenue Agency tax assessment to prove their place of residence.

The specific nature of the $1,691 in Ottawa expense Duffy claimed are unknown. Under the current financial reporting system, the Senate provides only aggregated totals for each category of expense. That will change next quarter as the Senate moves to a more transparent and detailed public accounting of each senator’s costs.

Duffy's amount was far less than most other senators, who collectively averaged more than $6,164 in National Capital Expenses over the four-month period. Duffy, however, was not sitting while his trial was under way, for much of the same period.

Senators Jim Munson, Anne Cools and Thanh Hai Ngo were the only members of the Red Chamber who did not file claims for time in Ottawa.