Former Rep. Michael Grimm will start his eight-month prison sentence for tax fraud on Tuesday, Sept. 22, 2015. View Full Caption DNAinfo/Nicholas Rizzi

STATEN ISLAND — From congressman to inmate number 83479-053.

Michael Grimm, 45, will turn himself in and start his eight-month prison sentence for his tax fraud conviction on Tuesday. He'll serve it at the medium security FCI McKean in Pennsylvania.

The start of his sentence was delayed by 12 days after a judge approve his request to push back his surrender date so he could have an undisclosed surgical procedure.

In July, Grimm — a Republican who represented Staten Island and parts of Brooklyn in Congress — was ordered by Judge Pamela Chen to serve the eight-month sentence with a year probation and 200 hours of community service.

He was convicted of underreporting profits from an Upper East Side eatery he co-owned before he was elected to Congress.

Through filings and statements in court, Grimm and his lawyers tried to paint an image of a dedicated servant to the country — with years in the FBI and the Marines — and caretaker to his mother, sister and former Borough President Guy Molinari.

But Chen chided Grimm for his crime, belatedly apologizing for it and characterizing tax fraud as a minor offense.

"Your moral compass, Mr. Grimm, needs some reorientation," Chen said during the sentencing.

"He was actively perpetrating fraud on a regular or weekly basis."

In 2014, Grimm was hit with a 20-count indictment for underreporting profits from the restaurant on tax returns from 2007 to 2010.

He pleaded guilty to the charges in December and stepped down from his post in January — setting off a special election for his seat eventually won by former District Attorney Dan Donovan.

In addition to the prison time, Grimm also agreed to pay back nearly $150,000 to the government as restitution for his tax fraud.