Some Capitol Police officers didn’t get holiday pay for working on Inauguration Day, despite a memo from Chief Phillip Morse assuring them that they would.

Union officials plan to file a grievance this week asking for the additional pay or an extra eight hours of leave. Officers, they say, should get the same treatment as their peers in agencies such as the Metropolitan Police Department and the Secret Service.

Not following suit — and worse, backtracking on a promise — sets a dangerous precedent that could affect morale, said Jim Konczos, executive chief steward of the Capitol Police Labor Committee.

“Events like that are a headache and inconvenient for a lot of people,” he said, adding that all officers were required to be on duty.

A Jan. 23 memo, signed by Morse and obtained by Roll Call, declares that Inauguration Day “was designated as a holiday for pay purposes for USCP employees.” That would mean double the hourly wages for eight of the 16 hours many officers worked on Jan. 20.

The extra pay for each officer would have been minimal — roughly somewhere from $150 to $250 depending on their salary, according to Konczos.

Some officers got that pay for the day before Inauguration Day, which was Martin Luther King Jr. Day and thus a federal holiday. They would also have collected overtime pay — at time and a half — for any hours beyond a normal eight-hour shift.

In past years, the two days haven’t landed successively, a fact that could significantly jack up the payout to officers.

For example, if all of the approximately 1,000 officers in the union got $150 in holiday pay for both days, that alone would cost about $300,000. The department was prepared to spend close to $2 million on overtime costs for the inauguration and its preparation, though it’s unclear whether holiday pay would factor into that.

Capitol Police officials did not return repeated calls for comment, but in the past, spokeswoman Sgt. Jessica Baboulis has declined to comment. Holiday pay, she said, was a “personnel matter.”

Since Jan. 20, officers have said they were unsure whether they were getting the bonus, mostly because of contradicting announcements during roll call.

Konczos said the department hasn’t officially released an explanation, but that one supervisor said it was a trade-off. Officials, he said, raised the cap on how much overtime an officer is allowed to do from Jan. 18 to 31, and thus holiday pay for Jan. 20 was eliminated.

At the very least, Konczos said, officers should get the same perk as federal employees who didn’t go to work on Jan. 20: an extra day off.

“I would very disheartened if I find out that Human Resources, who’s behind all of this, got the day off,” he said.