Pulrose Post Office will close next month.
It follows the announcement that sub postmaster Alan Clucas is retiring.
He’s run the office, on Alder Road in Douglas, for the last 20 years but his post will not be advertised.
Post Office Chairman Julie Edge says: "We accept Mr Clucas’s decision to retire and wish to express our sincere thanks to him for his exemplary loyalty and dedication to providing postal services to customers for such a long time.
"We recognise that customers will be saddened by the news and I’ve no doubt he will be much missed by his customers.
"Mindful of the change this will have on MiCard customers in particular, we are working closely with the Social Security Division and are in touch with the MHKs for Douglas South, Bill Malarkey MHK and Kate Beecroft MHK, to ensure disruption is kept to a minimum."
Mary Gaffney, General Manager for Retail and Customer Services, says: "We are ensuring the needs of customers are met and are in contact with the relevant organisations to help manage the change.
"We wish to ensure steps are taken to make the transition for customers to collect welfare payments from a different nominated post office is as smooth as possible.
"MiCard customers can, if they wish, choose to nominate a person to collect benefits/pensions on their behalf by way of a proxy.
"The Social Security Division has sent a letter to all their MiCard customers explaining the process they should follow."
The Isle of Man Post Office says customers should now use the post office in Anagh Coar or in Strand Street – both of which are on a bus route from Pulrose.