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A 101-year-old, retired FDNY battalion chief is one of more than 410,000 victims of a Medicare accounting flub that mistakenly double-billed customers for monthly premiums.

John Nasta was charged twice his monthly premium of $135.50 in a recent glitch that struck Medicare’s “Easy Pay” automatic payment system and impacted nearly half-a-million program recipients.

Lifelong friend Patricia McLaughlin, who has Nasta’s power of attorney said she only became aware of the issue after her own Medicare-beneficiary husband David Haight was double-charged.

When she checked, McLaughlin was horrified to discover that Medicare deducted $271, or double the $135.50 monthly charge, from Nasta’s account as well.

“It’s a big mistake. It’s kind of a miracle that I discovered it,” said Haight, 65. Medicare deducted roughly $1,000 from his Easy Pay account instead of $500 — his typical monthly premium.

The federal Centers for Medicare and Medicaid admitted the nationwide double-deduction snafu affected 411,000 beneficiaries of the government-run health insurance program for senior citizens.

The goof — which only impacted monthly August payments — could have sent the bank accounts of some fixed-income seniors into the red, potentially causing other checks to bounce, triggering costly bank overdraft fees and other penalties.

In a statement to subscribers Medicare admitted the error.

“Due to a processing error a small percentage of people who pay their Medicare premiums through Easy Pay had their premiums deducted twice from their bank account. Medicare is currently working with the Treasury Department to reverse the duplicate premium deduction and have the erroneous deduction credited back to accounts, as soon as possible. If you are concerned about overdraft or other fees related to the issue, you should contact your bank and ask that fees be waived,” the agency said.

But McLaughlin said it’s not that simple.

“It’s concerning that the government is taking this so lightly. Banks aren’t so willing to forgive fees,” McLaughlin said.

“It’s ridiculous,” Haight added.

McLaughlin worried that many elderly Medicare participants aren’t as adept at using computers to check on their banking activities, saying the problem could go unnoticed or be harder to address if a recipient doesn’t have a computer.

Also, the government deducts Medicare premiums directly from the monthly Social Security payments to senior citizens who no longer work, leaving them with less monthly income for living expenses, she said.

McLaughlin said the government should have a dedicated phone hotline for Medicare recipients to contact.

Nasta was feted last year during his 100th birthday celebration.

Additional reporting by Emily Saul