Nearly a third of people risk falling victim to fraud by writing down pin numbers for their credit and debit cards, a survey claimed today.
And if they lose money as a consequence, they may not be covered by the Banking Code.
In research carried out for card product maker cardextras.com, around 32% of people said they kept a written record of their pins, with 27% admitting they made no attempt to disguise what the number was for.
The research found that following the roll-out of chip and pin credit and debit cards, people now had so many pins to remember that 40% said they had forgotten their pin when trying to use a cash machine or buy something.
At the same time, 18% of people said they tended to favour using one card over others because then they only had to remember one pin.
Despite being able to change their pin to something they could remember more easily, only 30% of people said they had altered it.
"The introduction of chip and pin is a welcome measure in the fight to reduce fraud," said Christine Lawton, of cardextras.com.
"However, as cardholders struggle to remember a variety of different pins, there is a danger of an increase in the risk of fraud as people write down their pin numbers without disguising them."
Commenting on the research, Mark Bowerman, spokesman for the card issuers' trade body Apacs, said it was "never a good idea" to write down your pin and warned that there could be costly consequences.
"UK card customers are protected against loss or fraud by the Banking Code which says that you are covered as long as you haven't acted negligently or fraudulently. One of the things the Banking Code regards as negligence is writing down your pin."
He suggested cardholders change the number given by their card provider to they could remember - an anniversary for instance, but not a birthday - or use a four-word phrase to help them remember.
"For example you could use the phrase 'I love my wife' and work out how many letters are in each word. This would help you remember the pin 1424."
Mr Bowerman advised against using a single pin for all credit and debit cards, but said this would not be considered negligence and "it's a lot better than writing your pin down".
More than 100m chip and pin cards have been issued in the UK since the scheme was first trialled in May 2003.
According to Apacs, by the end of 2005, around 90% of cards will be chip and pin and 90% of retailers' tills will be pin-enabled.
Apacs has produced a guide to remembering your pin (pdf). To read it, click here
