Steven Lee, of The Stables, Rosemary Lane, Bartle, Preston, was investigated by Lancashire Trading Standards over a failure to give cancellation rights for roofing and building work to a couple, and misdescribing and failing to complete work he had been paid for.
The offence dates back to June and July 2018.
The 67-year-old, who has a chequered history of similar crimes, admitted the consumer offence in a hearing before Preston Crown Court.
He and another member of his family were previously convicted of conning pensioners into paying vastly inflated bills for unneeded work on their homes.
Judge David Potter adjourned the case for his sentencing to July 9.