Call it judgment day. It looks like the Obama administration might yet face some kind of reckoning — in Congress, at least — over its payoff of a long-simmering claim to the Iranian regime.

That’s because to do so, the administration tapped a little-known account at the Treasury Department called the Judgment Fund. It is a special account used to pay out claims against the US government.

The details of how the administration did this, however, are being treated like a state secret. The State Department spokesman has clammed up tighter than a conch in a mudslide.

The topic erupted at the State Department’s daily not only on Tuesday but also today. This was after Claudia Rosett reported in the New York Sun that the administration made 13 transfers of $99,999,999.99 each.

Those payments add up to 13 cents shy of $1.3 billion. They were made January 19, two days after President Obama announced he’d cut a deal with the mullahs for $1.7 billion to avoid an adverse judgment at a court in The Hague.

We know, thanks to the Wall Street Journal, that $400 million of that was made in foreign currency, loaded on wooden pallets and delivered in a special cargo plane and functioned as a ransom payment to the mullahs, who had been holding a group of Americans hostage.

The remaining $1.3 billion only started to come into focus when Ms. Rosett discovered the 13 transfers totaling $1.3 billion on a Treasury Department Web site related to the judgment fund.

She sees no other explanation than that the payments, which went from Treasury on behalf of the State Department, were to cover the Iran settlement.

State’s daily briefing Tuesday was opened by the dean of the Foggy Bottom press corps, Matt Lee of the Associated Press. He called the settlement payments “the story that doesn’t seem to want to go away.”

Persistent as Mr. Lee was in his questioning, he could get bupkis out of the department spokesman, Mark Toner. He conceded nothing except that the Treasury Department was even less transparent than State.

This window into the shenanigans the administration is using to implement its deal isn’t just about whether the latest move is legal. No one has yet said it broke the law.

One of the principles of newspapering, though, is that the scandal is often not about what’s illegal but what’s legal. How can the administration tap the taxpayers for $1.3 billion without the say-so of Congress?

This is one of the most basic prohibitions in the Constitution. “No Money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law,” is the way the parchment puts it.

The government maintains the judgment fund is legitimate. It calls it an “indefinite, permanent appropriation.” The idea is that Congress didn’t want to be bothered with having to pass a law for every nickel-and-dime settlement.

Could it have intended to authorize a blank check to send $1.3 billion to a regime that calls us the Great Satan and threatens to wipe Israel off the map? What Congress in its right mind would do such a thing?

What makes it so galling is that the administration knows that had the Iran payments been submitted to Congress for approval, they would’ve been turned down. Majorities in both houses were against the entire Iran nuclear deal — which is why it was treated as an executive, unilateral action and never submitted to the Senate for ratification as a treaty would have to be.

And this is why the State Department and the Treasury are playing dumb. On the line is the constitutional good faith of President Obama, Secretary of State Kerry and Treasury Secretary Lew.

Not to mention Hillary Clinton. She seems to be hoping that she can get all the way to November without having to answer for the appeasement of Iran that started on her watch and that she’s endorsed.

I opposed even the initial talks with Iran, because history has taught that the talking itself begets the appeasement. Once it starts, the appeasing party — in this case the administration — keeps getting sucked in for more.

No wonder that within hours of Ms. Rosett’s story appearing on the Web, The Post, in an editorial, predicted that the matter would prove to be “a rich trove for congressional investigators.” You can, as the Sun said yesterday, bet your last $99,999,999.99 on it.

A version of this column first appeared in the New York Post.