The PSNI is spending £100,000 a day on overtime as it struggles to cope with a depleted workforce.
In some cases, officers claimed more than £40,000 on top of their normal salary for working extra hours.
The total bill for the last three years topped £124m.
One officer worked an astonishing 1,759 hours of overtime in a single year.
The PSNI is preparing a report for the Policing Board on the costs, with one board member voicing concern.
However, Mark Lindsay, who chairs the Police Federation for Northern Ireland (PFNI), said the spending reflected a service that was "under-resourced from the start".
Figures obtained by this newspaper show:
It is estimated that the PSNI is short of almost 800 officers to provide an effective service.
In August this newspaper revealed how Chief Constable Simon Byrne was facing a backlash from officers over attempts to clamp down on overtime across the force.
It was proposed that officers would be required to work on their rest days with the promise of a day off in lieu some weeks later.
PSNI employees have also not yet received a pay rise dating back to 2017/18 that has already been handed out to their counterparts across the rest of the UK.
Ulster Unionist MLA Alan Chambers, who sits on the Policing Board and is a former part-time RUC reservist, said board members are aware of overtime spending.
He said it was a concern for the PSNI and board members.
"It has been the subject of quite a lot of discussion in the Policing Board," he said.
"The PSNI set up a committee within the organisation to report back to the Policing Board to say what they were going to do to try and address this.
"The Policing Board are aware of it and we are concerned. We are concerned for the welfare of the officers doing it."
Assistant Chief Constable Mark Hamilton noted that overtime spending had fallen in each of the last three years without a reduction in services.
He said overtime is inevitable in an organisation that faces "unpredictable and critical demand".
"Overtime will never be a default option to meet a resourcing demand and we recognise the additional burden it puts on our workforce," he continued.
"We constantly review our resources to ensure we keep the public safe.
"Due to peaks in demand and the often unpredictable nature of policing, police officers across the whole of the PSNI - including our specialist services - are expected to work extra hours in order to keep people safe. This may entail working additional hours on top of their normal shifts, rest days and public holidays.
"As an organisation we seek to manage this in a way that both meets the demands on us and also provides for the welfare of our people," he added.
The Police Federation, which represents rank-and-file officers, said those receiving the highest overtime payments are not regular officers but those in specialist departments, who are critical in "saving lives".
Mr Lindsay also said the vast majority of officers working additional hours would much rather be at home with their families.
"You have the Chief Constable, the Policing Board and ourselves saying that we're at least 800 officers short of what we need," he continued.
"While the overtime budget and overtime hours are high, we have thousands of officers being affected by having to modify their rest days.
"Their days off are moved at no cost to the organisation when they aren't being paid overtime.
"While the overtime budgets are high, it's the strain that's on the organisation at the minute around budgets that are leading to this, and those figures, while they're well managed, are absolutely necessary.
"These officers are making a massive sacrifice through their days off and the days they're losing as far as rest days are concerned," Mr Lindsay added.