Jitendra Karia said two unknown men assaulted him before tying him up after entering Clifton Post Office in Preston Old Road on September 18, 2019.
The 49-year-old then claimed the two offenders held him at knifepoint before stealing a large sum of money from the safe.
Police were called to the scene at around 5.40am after the shop's alarm alerted nearby neighbours.
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Detectives launched an investigation but soon established the postmaster's story was "impossible" after examining CCTV footage.
The footage - which had been seized from a neighbouring property - showed no one entering or leaving the building apart from Karia.
Karia was arrested by police and later given summons to appear at court. He pleaded guilty and was jailed.
DC Angela Scanlon, of Blackpool CID, said: "For reasons only known by Karia he concocted a story claiming he had been robbed by two men.
"This initially appeared to be a very serious offence and led to a substantial police response as officers worked hard to find the offenders responsible.
"Significant resources were diverted to help the investigation but following a review of CCTV, Karia's story was quickly found to be untrue and his lies exposed.
Karia, of Stanagate, Clifton, was sentenced to 15 months in prison at Preston Crown Court on Wednesday (August 25) after admitting an offence of committing an act with the intent to pervert the course of justice by making a false complaint of robbery.
"It goes without saying, Karia, as postmaster, held a trusted position within the community which he has breached," DC Angela Scanlon added.
"The false report he made will undoubtedly have caused unnecessary worry and uncertainty within the local community.
"It was pure fantasy and I am pleased he finally admitted his guilt at court."
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