New York City’s overtime bill hit $1 billion in the final six months of 2021 — a 62 percent jump compared to the previous year, state Comptroller Tom DiNapoli said Wednesday.

Speaking to a virtual meeting of the Association for a Better New York, DiNapoli pinned the $385 million spike on the combined impact of COVID-19 on the city’s budget and workers.

“During the height of the pandemic attrition was lower than average but hiring was frozen for many positions. Since mid-year 2021, however, the attrition has risen,” DiNapoli said. “Reduced staffing compounded by COVID-related absences led city overtime to exceed a billion dollars the first half of the year.”

The majority of the total OT tab — 83 percent — went to employees of the police, fire, corrections and sanitation departments, the report said. All four agencies face “significant overtime risk,” DiNapoli told business leaders.

The drop in municipal headcount counters eight years of workforce growth, primarily at the NYPD and Department of Education, according to the report.

The drop has been most significant among specific titles among school safety agents, whose ranks dropped 20 percent from June 2020 to November 2021, and corrections officers, whose numbers shrank 17 percent. Other positions whose numbers plummeted included teaching assistants, managers and administrative support, the report said.

Yet just two departments — Correction and Investigations — told the comptroller’s office that lower staffing levels were “impacting [their] ability to provide certain services,” DiNapoli said Wednesday.

The reduced headcount gives Mayor Eric Adams a head start on his goal to cut agency budgets by at least 3 percent, he told business leaders — but the city could face significant challenges as federal COVID-19 relief dries up.

“On one hand, the staffing decline gives the city a chance to re-examine its workforce, restructure programs with greater efficiency and achieve that 3 percent cost savings directed by Mayor Adams. However, it could adversely impact the quality and consistency of some public services and programs,” he warned.

“Sharp declines in the city’s workforce combined with uncertain revenue to pay for programs as federal aid winds down may test the city’s ability to deliver high-quality services, just as the city is trying to ensure a healthy and broad recovery.”

City Hall did not immediately return a request for comment.