Mayor Eric Adams has opted against using an established federal program to recoup the $1 billion the Big Apple may spend to house and care for more than 20,000 migrant arrivals because of… paperwork.

Top officials made the astonishing disclosure during a Tuesday budget briefing where they revealed that City Hall had only filed $4.8 million in expenses to be reimbursed so far — and received every dollar that they’d formally sought.

The hangup, the officials revealed, was that the Adams administration is now seeking a special $1 billion grant from the federal government upfront to cover migrant-related expenses, instead of using the established reimbursement program to cover expenditures already made.

The grant, they added, would allow City Hall to avoid much of the paperwork typically associated with seeking reimbursement, including providing receipts and other documents.

Officials said the administration hasn’t even finished drafting its formal request for the billion dollars to the Federal Emergency Management Agency, which also administers the reimbursement program for migrant-related expenses.

They added that they have held “informal” conversations with New York’s congressional representatives and Gov. Kathy Hochul on the matter.

Officials made the admission during a budget briefing for reporters on Tuesday, who were only allowed to attend on the condition that they would not cite the officials by name and that quotes could only be paraphrased.

The information stood in sharp contrast to Hizzoner’s frequent excoriations of state and federal officials for not providing rapid reimbursement — statements in which he’s never mentioned the decision to seek an alternative to the traditional reimbursement program.

“We are still fighting for reimbursement,” Hizzoner said. “We think that the campaign season is over. It’s time for people to focus on this issue. We need to be reimbursed.”

Adams then added: “We spent a great deal of money for a national problem, and we are looking for reimbursement and assistance from the state and from the federal government.”

He later attempted to argue that Gov. Kathy Hochul and President Joe Biden’s campaign schedules amidst the midterms had likely slowed the consideration of the city’s request for aid.

“When I say campaign season is over, people seem to be more focused on issues when they don’t have to run around from location to location to location,” Adams said.

“Not campaign season is over because no one wanted to talk about it — because I was talking about it,” he added. “But it seems like people get more focused when they’re not running around from one location to the next.”

The billion-dollar figure itself is a source of controversy.

An analysis by the Independent Budget Office put the price tag for the crisis at $600 million for the 2023 budget year, which runs from July to June.

Adams even backed off the $1 billion price tag temporarily while talking to reporters when he was in Puerto Rico over the weekend.

Additional reporting by Bernadette Hogan