IF YOU have trouble remembering your PIN, spare a thought for the seniors in the community.

As of today, they won't be able to sign for their credit card or debit card purchases.

National Seniors Australia (Garden City) branch president Hazel Gillies said she was worried about how the change would affect those with dementia or the beginnings of the disease.

The change comes into effect today and cardholders will need a PIN to complete their transactions.

"I'm not worried about myself as I've been using a PIN for years," Mrs Gillies said.

"But I think the older ones would have a problem remembering (the PIN), particularly those with dementia, will have trouble.

"I don't know any way around it and that's the main problem I see.

"They'll write it down so they won't forget and that'll be in their handbag or wallet if it gets stolen."

Mrs Gillies said the situation must be one which worried families.

"It's harder if you have a few (accounts) because they tell you to have different numbers," she said.

Heritage Bank chief executive officer John Minz said the change applied to all institutions across the country, not just Heritage.

He said the change was about adding an extra layer of security, particularly when cards were lost or stolen.

"Your PIN transaction is encrypted and sent in real-time to your card issuer to be authorised," he said. "This makes it more difficult for fraudsters as they need to get hold of both the card and the PIN to be able to misuse it."

The PIN requirement does not apply to "tap and go" purchases.