The central bank said it sold $37.6 million at a cut-off price of 7.1401 pounds per dollar, the same as its price in its last sale, on Monday.
On the black market the dollar changed hands at 7.38/40 pounds, the same rate as a day before.
The rate for dollar sales has stayed in a tight range since the beginning of June, after the bank allowed the pound to weaken in May. It had offered $40 million on Wednesday.
The rates at which banks are allowed to trade dollars are determined by the results of the central bank sales, giving the bank effective control over official exchange rates.