The report from the Parliamentary Budget Office (PBO) released Wednesday shows wide variances in how much sick leave is taken from one department to another.
But parliamentary budget officer Jean-Denis Fréchette says most departments don't have policies to backfill for sick leave.
That means most sick employees are not replaced, resulting in no incremental cost to departments.
The governing Conservatives have been looking to cut the cost of public-service salaries, pensions and sick leave as part of efforts to balance the federal budget by next year.
The new report was requested by NDP MP Paul Dewar after the PBO estimated this February that the fiscal impact of paid sick leave in the federal public service was $871 million in 2011-12.
The report instead found there is "a notable variance among organizations in the use of sick leave," and that the cost of paid sick leave "was not fiscally material and did not represent material costs for departments in the CPA."
But the report also notes that data from some departments were incomplete, and sometimes unavailable.
The Canada Border Services Agency, for example — which was expected to have high sick leave costs because officers need to be backfilled for operational, health and safety reasons — said it does not track data on backfill costs due to sick leave.
The report also found:- Correctional Service Canada logged the most days of paid sick leave, at 14.6, in 2011-12.
- The Department of Foreign Affairs, Trade and International Development had the lowest number, at 7.7 days.