The Labor Department’s watchdog office is still investigating the agency’s handling of a regulation for tipped workers almost nine months after it first announced it would do so.

The Office of the Inspector General will continue looking into the Wage and Hour Division’s “tip pool” rulemaking process this fiscal year, as well as the division’s enforcement procedures, the OIG said in its Office of Audit Work Plan for FY 2019. The OIG intends to continue its audit of the Office of Federal Contract Compliance Programs as well.

An OIG spokesman said the office doesn’t yet have a set date for...