Parliamentary authorities say they are too busy preparing to defend the building's visitors' car park from being overrun by public servants from July this year to turn their attention to paid parking in the "private" car parks in the massive building.

Paid parking will be introduced in the Parliamentary Triangle on July 1, forcing bureaucrats who work there to pay $11 a day and sending the area's national institutions scrambling to protect their visitors' parking areas from being taken over by office workers.

Employers in the area face a choice of charging their workers for parking or incurring a fringe benefits tax liability on the perk.

But the secretary of the Department of Parliamentary Services, Carol Mills, told The Canberra Times that the thousands of workers in Parliament House were unlikely to face crunch time until April next year, the start of the FBT period for the year.

Meanwhile, Governor-General Quentin Bryce has signed the legal document ceding power over the triangle's parking to the chief executive of the National Capital Authority, removing all doubt over who will enforce the unpopular new regime.

But Ms Mills said the parliamentary workers need not worry - at least not for a little while.

"We're treating it as a separate issue because it doesn't have the same time imperative of the first of July," Ms Mills said.

"We're not driving this ourselves, we're working out how best we respond to the decision elsewhere in the triangle.

"If there is a liability that accrues to the private car parks because of the NCA policy, then we have until the FBT year to work out how we might respond."

Ms Mills acknowledged that assessing FBT implications, which depend on the distance between the employer-provided car park and a paid-parking operation, for about 2500 workers in Parliament House who answer to dozens of different employers would be "complex".

"We want only to look at the arrangements in the private car parks in the context of whether employers will become liable for FBT because of the proximity to the NCA parking," Ms Mills said.

"If that were the case, yes, it is going to be a complex issue because we do have so many employers in the building."

But for now, the focus is on bolstering the defences of the Parliament House visitors' car park against public servants expected to pounce after July 1 on any opportunity to avoid the $11 a day fee.

"The public car park is our highest priority because that comes in on the first of July, our focus has really just been around what model can be put in there that discourages long-term parking," Ms Mills said.

"It needs to be done in a way that doesn't discourage short-term visitors to the building."

The rules need to give tourists ample time to take a one-hour official tour of Parliament House but not long enough to give a desperate bureaucrat a whiff of opportunity.

"You've got to allow at least that amount of time, we don't want people to feel that they're rushed when they visit," Ms Mills said.

"On the other hand, we don't want to make it such a long period of time that long-term parkers might take a gamble, saying 'I'll park there and hope I don't get booked.'"