New Delhi District Consumer Disputes Redressal forum, presided over by C K Chaturvedi, asked the firm to pay Rs 1,49,783 to Noida resident Rajesh Kukreja.
It also said that the firm "unjustly enriched" itself by "deducting brokerage".
"We hold OP (firm) guilty of deficiency in unlawful trade practices and direct the OP to... Refund Rs 1,49,783 wrongly deducted as brokerage," the forum said.
Kukreja had told the forum that he had booked the property in firm's residential project in Gurgaon by paying Rs 26.82 lakh in 2008.
The reality firm, however, refunded him only Rs 25.32 lakh by deducting Rs 1,49,783 as brokerage cost.