A London council is marking 125 successful prosecutions against agents, landlords and sub-letting tenants since 2016.
The authority, Brent, says the convictions have resulted in more than £730,000 in fines.
In addition, more than £100,000 worth of civil penalties against rogue landlords, agents and sub-letters have been issued since their introduction in September 2017, with the council collecting £63,500 of these fines to date.
In the latest conviction, a landlord has been slapped with £7,400 in costs and fines after failing to pay for a £340 five year selective licence.
The unlicensed two bedroom flat in Harlesden came to the attention of enforcement officers after the family complained to the council about their broken boiler.
Errol Roy Thompson of Bedford pleaded not guilty at the first hearing in August last year but changed his plea to guilty at the trial at Willesden Magistrates Court this month.
Thompson had begun to fill out an application for a selective licence in June 2016 but had failed to complete and pay the licence fee.
A council spokesman says: "Mr Thompson was also sent a letter which specifically told him his property required a selective license. His failure to pay £340 has resulted in fines of more than £7,000 and a criminal record. The law is clear.”