Why isn’t state Attorney General Barbara Underwood looking into that bizarre $531,000 payment to the Rev. Al Sharpton by his own nonprofit for his “life story”?

Tax and film-industry experts contacted by The Post all raised their eyebrows after learning the details.

And Sharpton’s long history of dubious fiscal management and hefty tax liens — not to mention two mysterious fires that conveniently consumed his financial records — doesn’t exactly inspire confidence that all this is on the up and up.

Moreover, as The Post’s Melissa Klein has noted, the way this transaction was listed in a tax filing by the National Action Network raises questions about NAN doing business with its own president.

The AG’s charities bureau is supposed to investigate such “related party transactions.” But Underwood’s office failed to return at least two messages seeking comment. And no other state agency seems to be looking into the matter.

Sharpton said he sold his life story to guarantee NAN income after he retires. But experts don’t see those rights as something Hollywood would pay much for, despite his claim (with no details) of projects in the works.

So it looks like the only one likely to reap a windfall here is Sharpton himself.

The Rev insists an individual (whom he won’t name) put up the cash, and the deal was initiated by two board members (whom he won’t name) and “independently approved” by NAN’s executive committee (as if any NAN committee could act “independently” of Sharpton).

Sure seems like Underwood’s folks should at least be asking a few pointed questions — and doing so before longtime Sharpton pal Tish James takes over the AG’s office Jan. 1.