There's no such thing as free advice

A doctor and an accountant were seated together at a formal awards dinner.

The accountant watched bemused as the guy sitting on the other side of the doctor sought his advice about how to alleviate his back pain. The doctor gave some medical advice, then turned to the accountant and continued chatting with him. Later he confessed "I really hate it when people seek free advice from me at parties."

The accountant replied "I know exactly what you mean. It happens all the time to me too."

"How do you handle it?" asked the doctor. "It seems rude not to answer when you are asked for your advice at a social gathering."

"Simple" said the accountant. "I give a little advice and the next day I send them a £50 bill for consultancy services".

"What a great idea" said the doctor. "I think that would work for me. I must remember to try it." But by the time he got home he'd already forgotten about sending a bill to the man with the back pain.

He remembered the next morning though when he opened his post. In it was note from the accountant with a bill for £50!

This is a joke I've told many times over the years, since long before I found a version of it in the book Revenge of the Taxpayer