A pair of New Jersey businessmen are facing prison time for allegedly ripping off the United States Postal Service to the tune of $6 million by altering postage labels through their Amazon shop.

Jack Koch, 44, and Steven Koch, 43, are accused of using the doctored labels to ship the household products they sold on Amazon for a cheaper, flat rate, the feds in New Jersey said Tuesday.

To do so, the men bought flat-rate envelope postage labels meant for USPS-produced compact envelopes — and allegedly removed the required “FLAT RATE ENV” endorsement.

That allowed them to ship awkwardly shaped products, like bottled water, laundry detergent and cases of soda in big boxes at the more affordable, flat rate.

Court papers unsealed in New Jersey federal court say the Kochs’ alleged scheme cost USPS at least $6 million in postage revenue.

The USPS requires the “FLAT RATE ENV” message to appear on all mail pieces under 70 pounds that are sent using the discounted rate. Other mail pieces don’t need to bear labels showing pre-paid postage.

Jack, a k a Ismail Yilmaz, of Elmwood Park, and Steven, a k a Selim Memis, of Pompton Lakes, allegedly purchased 240,471 USPS Priority Mail labels, almost all for flat rate envelopes, through their business Fresh N Clear between January and September, the feds said.

Yilmaz had formally changed his last name to Jack Koch, though it was unclear whether Memis had don the same — or if the men were related.

The feds raided Fresh N Clear’s warehouse and found 223 of 225 priority mail parcels with fraudulently altered labels. Steven allegedly admitted to investigators that he, Jack and a cooperating witness who wasn’t identified in court papers had “cleaned up” the labels to ship their items.

The Wood Ridge-based company does business as “Better Shopping” on Amazon and sells hundreds of items in bulk like dry shampoo, tea, Comet bleach powder and Q-tips.

They are each charged with one count of theft of government funds, which carries a maximum of 10 years behind bars, and one count of postage stamp fraud, which carries a maximum of five.

The pair were scheduled to appear in court Tuesday afternoon.

A call to Fresh N Clear’s number went unanswered. The Kochs’ attorney information wasn’t immediately available.