And Valerie Costin's horror turned to embarrassment when the correspondence from Medway Council revealed the man was dependant on income support and did not have a penny in his bank account.
The mistake was uncovered when the mother-of-two opened the letter from the business support department about miscalculated council tax.
Valerie Costin, from Chatham, was sent a stranger’s council tax details
Mrs Costin, of Castle Road, said after numerous calls to the council she was told the blunder was probably caused by the wrong paperwork being stapled together.
The 44-year-old full-time carer said: "They asked me if I wanted a written apology. I said all I wanted was a guarantee that this does not happen again."
"I was sifting through the pages and I thought 'what's this?', and then noticed that this man's letter was attached to mine.
"I know it sounds selfish, but I'm glad it was not the other way round. I would be mortified if somebody had received a letter with sensitive information about me.
"You don't have to be Einstein to see this is a blatant breach of the Data Protection Act..." - Valerie Costin
"You don't have to be Einstein to see this is a blatant breach of the Data Protection Act.
"This poor man is probably blissfully unaware that I know all this about him."
A Medway Council spokesman said: "This was a genuine human error, which we are treating seriously as a data breach. We have apologised in writing and have put additional checks in place to prevent it happening again."
Council officials were also forced to apologise after writing to a man shortly after his death, telling him his benefits were being stopped because he had died.
The family of Leonard Green, who died in February aged 87, complained after reading his council tax benefit had been suspended "because of a change of circumstances".
The letter, addressed to Mr Green at his Gillingham home, went on to state the reason for the suspension was because the "customer has died".
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