Drivers who received renewal notices during the month of August as part of the government's short term vehicle registration scheme were overcharged, after the fee was reduced from $25 to $15.

The lower price, for Canberra drivers who register their vehicles for less than 12 months, came into effect from September 1.

A spokeswoman for the ACT Government's Justice and Community Safety Directorate said the incorrect fee had been included on registration renewal notices due in the period of September 1 to October 12.

The administration nightmare - expected to cost taxpayers thousands in postage and work hours - was caused by "human error".

Some of the 3600 drivers caught up in the mistake have received letters and refund cheques in the mail already.

Information was released to car owners on September 24 and one driver said she initially mistook the refund notice for a fine.

"Clients who have already paid the higher surcharge will be refunded the overpayment of $10," the spokeswoman said.

"Clients who pay through Canberra Connect or the website will be requested to pay the correct short term registration fees. Anybody who overpays through other payment forms will be refunded the overpaid amount." 

Any driver who paid the $25 amount through Canberra Connect shopfronts or the website can choose to use the money to offset another Road Transport Authority payment or can request a refund of the amount.

The spokeswoman said a staff member became aware of the error when a client attempted to renew their vehicle registration on 1 September.  Automatic refunds are now taking place.

Drivers were hit with a broad range of fee increases as part of this year's ACT Government budget.

The cost of drivers' licences, number plates and parking permits all increased from July 1.

Commuters parking cars around Canberra saw a 3 per cent increase in fees, contributing to an expected revenue haul of $17.8 million this financial year.

The cost of a five-year full ACT driver's licence rose from $161.70 to $167.10, while a one-year probationary licence increased to $189.50, up from $183.50.

A 6 per cent rise in traffic and parking fines was added, with another 6 per cent expected each year after that until 2017-18.

With a 3 per cent increase for parking, an all-day ticket issued by the ACT Government Road Transport Authority for a city outdoor multi-stay carpark has increased by 50 cents to about $14.

One hour of parking now costs drivers about $1.95.