Janet Harvey, a runner-up in the Money Grouse competition, found that charges on her Halifax Share Account led to a position where she owed the society 66p.
Halifax said in a letter that it was prepared to waive the 66p debt - as long as Mrs Harvey closed her account.
She said: 'If such a letter had arrived dated 1 April, I might have thought it was a wind-up. But presumably the Halifax is entirely serious and my small deposit is no more.'
Mrs Harvey's loss came more than five years after she opened an account at the Guildford branch of Halifax.
She said: 'I deposited pounds 12 when opening this account because I was returning to work at a play group. But I ended up working in a school elsewhere and the money was paid directly into my bank account.
'I forgot about my Halifax account and left it untouched. I heard nothing until a letter arrived, explaining not only had the entire balance disappeared but that I owed 66p.
'It just seems that all the money in my account has been used up to pay charges on it.'
The Halifax letter told Mrs Harvey that the latest quarterly charge of pounds 2.50 was being applied because her account balance was less than pounds 50 for a total of 30 days or more during the previous quarter.
A Halifax spokeswoman said the decision to make charges on low- balance accounts came in February 1992, when all customers were written to. Charges began in August 1992.
The charges were to reduce the disproportionate cost of managing small accounts and encourage their use. As a result, many small holders have been reminded that they have more than one account.
No customer holding an account before that time incurred charges without first being written to, giving three months' notice of Halifax's intention.
The spokeswoman said records showed that a letter was sent to Mrs Harvey on 17 February 1992, suggesting ways of avoiding the charges. The customer made no response and the first charge was made later that year.
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