A cleaner who accidentally received ￡90,000 in her bank account but did not tell anyone is now under investigation.
Comfort Konadu, 52, mistakenly received the sum when she went to return an item at a charity shop, a court heard.
A total of ￡90,047.19 was transferred to Konadu's account in error.
The cleaner did not tell anyone about the wrong transaction, but instead she transferred ￡57,000 of the cash out into other accounts, including to her children.
After discovering the error the bank were able to freeze and retrieve some of the money, but the Royal Mencap Society have lost more than ￡31,000, Manchester Evening News reports.
A Proceeds of Crime investigation is set to take place to establish whether the charity can recover any of its losses.
A judge told Konadu: "You have brought shame on yourself, and I dare say to your family."
Manchester Crown Court heard that mum-of-six Konadu had gone into the charity's shop in Openshaw, Manchester on Friday, October 11 last year to get a refund for an item she had bought.
Days later, senior managers at the charity - which supports people with learning disabilities - were alerted to the large refund and launched an investigation.
They contacted staff at the Openshaw store, who said there had been an "issue with the machine".
Two members of staff were suspended following the investigation, and they were later dismissed.
The charity were told that they would be liable for the loss because the incident had been a result of an error.
Prosecutors said the sum "landed" in Konadu's account on October 14, after the weekend.
The same day she transferred out more than ￡57,000 to different accounts including one belonging to her son.
Some of the refund was recovered by the bank, but the charity were left facing a loss of more than ￡31,000.
Prosecuting, Kate Gaskell said this would represent up to 18 months worth of profits for the charity shop.
At first, Konadu, of Mattison Street, Openshaw, claimed she had been expecting some money into her account.
But she later pleaded guilty to theft.
Prosecutors said it would have been "obvious" to her that the money had been sent in error.
She did not inform the bank or the charity about the money, the court heard.
Defending, Max Saffman said that Konadu, also a grandmother of 12, usually lives a "modest and humble" lifestyle working as a cleaner.
He said the money was "more than she could ever have dreamt of", and that "temptation got the better of her".
Sentencing, Judge Nicholas Dean QC said a "considerable punishment" in the case was Konadu's loss of her previous good character.
The judge told her: "This was in effect an unexpected windfall into your bank account.
"You ought at that stage to have reported it to both your bank and to Mencap.
"You fell prey to temptation and acted dishonestly.
"You leave this court with a stain on your character."
She was sentenced to 20 months in prison, suspended for two years.
A Proceeds of Crime hearing will be held in December.