Do you really know what you'll have to pay for that new car?

If you're in the market for a new car, you're probably used to hearing prices quoted – plus on-road costs.

But what does that actually mean?

While airline "drip-pricing" – the practice of adding on extra costs after a headline price is advertised – has been under intense scrutiny and fines have been dealt out, car dealers carry on the practice unabated.

On-road costs are added to the price of a car as an extra upon purchase, but in practice they cannot be avoided, so the advertised price is not what you actually pay.

READ MORE: Airlines risk prosecution over pricing tactics, lawyer warns

The extras cover things such as vehicle registration costs, a warrant of fitness, road user charges for diesel vehicles and sometimes the cost of putting petrol in the tank, grooming the car or any pre-delivery inspections carried out.

How much is charged varies depending on the make and model of the car.

These usually start at about $400 if they simply cover a 12-month registration fee for a car but can be much more.

This week, the on-road costs for a new Toyota Camry, advertised at $39,990 and up, were $1095. A new Honda Civic would have $795 added on.

Other countries are taking action. The Dutch competition watchdog has ruled that on-road costs must be included in the advertised price, or dealers could be penalised.

Its chairman said that people should be able to drive out of the showroom for the price advertised.

Jessica Wilson, from Consumer NZ said it was an example of potentially misleading drip-pricing, and her organisation was keeping an eye on it.

"The Fair Trading Act prohibits misleading representations about price. But the Act hasn't been effective at regulating drip pricing.

"We believe 'all-inclusive pricing' rules are needed. All-inclusive pricing would force companies to disclose the full purchase price upfront."

She said Consumer NZ members had been asked to get in touch if they had been stung by drip-pricing such as this.

A Commerce Commission spokeswoman said used cars had to be sold with a consumer information notice that stated the total price.

"The Fair Trading Act will apply to the advertising of on-road costs if they are misleading customers."

David Crawford, of the Motor Industry Association, said variation in on-road costs could be due to the different ACC levies charged, depending on a vehicle's make and model.

"On-road costs used to all be the same but now they are not."

He said buyers would probably prefer to have prices advertised inclusive of on-road costs but the industry had developed a practice of advertising them separately.