A Working Lunch fan has written to the programme to warn fellow viewers to draw up Enduring Powers of Attorney or EPAs, in case they lose their ability to make important decisions.
She ended up having to pay large fees on her father's behalf because he had not signed an EPA.
The document gives a friend or relation the power to direct the affairs of someone who suffers from what is called "mental incapacity".
Sue Amass's father suffers from dementia and is already incapable of making decisions or signing an EPA, so Sue has had to apply to become the 'receiver' in charge of his money and property.
The viewer from Wickford in Essex advises people in a similar situation to "act sooner rather than later."
"My mother knew that she would have to set up a power of attorney, but she thought it would be when my father reached a point where he couldn't sign his own name. Then we found out that actually that's when you can't appoint a power of attorney," Sue told Working Lunch.
COST OF BECOMING A 'RECEIVER'
£580 - Commencement and Appointment
£695 - Legal fees
£55 - Medical check
£250 - Administration
£105 - Account fee
£100 - Insurance
Instead, Sue was forced to apply to the Court of Protection to be able to manage her father's affairs, following rules policed by an arm of government called the Public Guardianship Office.
To get the process going, she had to pay £580 in fees to the Office, £695 in legal fees, and £55 for a medical check.
On top of that, she must pay fees totalling £455 every year out of her father's money, including a £250 administration charge.
If her father had pre-arranged an EPA himself when he could still sign it, then the cost would have been just £120 to register the power at the time it should take effect.
Power of attorney rules are due to change in England from October this year, when the Enduring Power of Attorney will be replaced by a new Lasting Power of Attorney.
However, existing arrangements will be allowed to continue.
People concerned can seek advice from Citizen Advice Bureau, the Alzheimer's Society, or from the website for the Public Guardianship Office.