Staff at NatWest wrote to "Noodles the Dog" to inform him he owed the branch £6.84 after his account became overdrawn. The official letter, which also asked the household pet to make contact within 14 days to discuss the situation, was sent to a home in Woodhouse Eaves, Leicestershire, at the beginning of the month.
However, the tenants had moved out months earlier, leaving the home's resident, Rupert Chapman, scratching his head when the request arrived.
Mr Chapman opened the bank's letter, hoping to gain some information about the account holder to allow him to forward the post.
Sensing an opportunity, he also replied to the bank with his own letter signed by his six-year-old labradoodle, Charley.
"She's not in debt, but she costs a fortune to keep," said Mr Chapman.
"When the letter came it was addressed to Noodles the Dog – it was clearly someone who was in the house before – and I had no idea what it could be.
"We moved in in August and the previous people had rented and I didn't know who they were, so I thought it would be fitting to send a reply from Charley."
NatWest said it did not expect Mr Chapman – or Charley – to cover the outstanding amount. It also explained it was not unusual for customers to name their accounts after their pets.
Bank spokesman Grant McDonald said: "We get a lot of accounts like this.
I worked in a branch years ago and people used to name their accounts after their animals and use them to pay for things such as vets' or kennel fees.
I did work for an branch where a dog owner had trained his pet to bring his pass book in and pay in money.
The new home owners do not owe the bank anything, this is the previous tenant's debt, so they shouldn't worry about it."