A buyer on the development complained to the Advertising Standards Authority (ASA) that the estimated parking and service charged per square foot per annum advertised in 2017 had been misleading.
In the brochure the developer had given estimates of a service charge for townhouses of £1.59/ sqft pa and parking at £308 per space per year.
Ballymore argued it was typical for the service charge to fluctuate in the first few years, especially where the development had phased handover.
It added the estimated service charge cost per square foot was based on a preliminary estimate from knowledge of the development and similar developments prior to completion.
Ballymore said after the ad had been published the service charge had been increased for townhouses from £1.59 to £1.89 per square foot.
The developer also acknowledged that the car park cost had changed since the ad and original budget was issued.
The ASA upheld the two complaints and noted the estimates had not provided information on how they may change over time.
In its ruling the watchdog said: “We considered that although consumers would understand that the figures were estimates and may change slightly, they would be based on a robust method of calculation and not change significantly.”
The ad must not appear again in its current form and the ASA told Ballymore to ensure it based its service charges on robust methods of calculation.