A DUBLIN based bicycle shop, run by the Fitzpatrick family, was served with the fine after daughter Erin offered to wash bikes.
The family behind the Dutch Bike Shop, in Goatstown, arrived into work on Wednesday to find a fine in the post from the local Dún Laoghaire-Rathdown County Council.
The posters, put up by Erin on June 9, asked for €3 for a bicyle wash and €4 for a wash and polish but it wasn't until June 13 that the owners of the bike shop realised the posters were a breach.
Astrid Fitzpatrick, Erin's mother said the children made little to no money on the day: "Erin made just over a tenner on the day, and we get hit with a €150 bill".
"I am not going to get cross with the kids, at least hey are being inventive, doing something useful instead of staring at a screen at home. They have to keep coming more [to the shop] often over the summer, and I don’t want them to get bored. Rather have them excited for earning some ice cream money," she added.
The Dutch Bike Shop said they were "feeling annoyed" by the fine and couldn't understand how the person responsible for sending the fine didn't see it was a "kid's sign".