The $29.4 billion deficit forecasted in last week’s federal budget raises a lot of questions – including how the government is going to whittle it down over the next five years, and what role, if any, further tax increases will play.

For Rhys Kesselman, the Canada Research Chair in Public Finance and a professor at Simon Fraser University, a primary question is whether the government actually wants $29.4 billion worth of economic stimulus.

If they do, then there’s no need to raise government revenues since it could limit the effect of the stimulus, he said this weekend.

Chris Ragan, a professor of macroeconomics at McGill and the chair of Canada’s Ecofiscal Commission, agreed there’s no need at this point to increase taxes as the government’s still in a “fine” overall fiscal position.

And – they have a plan to get back to balance.

The government’s “path to balanced budgets involves putting more money in the pockets of middle class Canadians and creating conditions for long-term economic growth,” said Annie Donolo, a spokesperson for Finance Minister Bill Morneau.

If the government’s plan works and the economy hits real growth rates of 2.5 to 3.5 per cent, there may be no need for further tax increases even down the road because a stronger economy will lead to higher revenues at current tax rates, Kesselman said.

But Kevin Page, the former parliamentary budget officer, didn’t express a lot of confidence in the government’s planning, calling its analysis around fiscal projections “weak” and “incomplete.”

Raising taxes may be the correct policy advice, he said in an email this weekend.

But the government would need to show the public that they’d tried to make up for lower revenues by allocating dollars more effectively and improving efficiency in order to gain any support for a major increase to revenues.

The government committed to undertaking a review of the federal tax system in the coming years – a review that’s long overdue according to Ragan.

“The late eighties, early nineties was the last time we took a close look at the tax system and over time it gets things added to it, budget after budget we generally add stuff to it and so the system just becomes more complex,” he said.

Examining tax expenditures – tax breaks like preferential tax rates, exemptions, deductions, and tax credits – will be a key element of the government review, which Kesselman said should assess whether each tax break is doing the job it was meant to do, and whether its purpose is justifiable.

The 2016 Report on Federal Tax Expenditures lists more than 180 different tax breaks, which will cost the government about $100 billion for 2015. About 50 of those tax breaks did not include cost projections for 2015 because there wasn’t any “data available to support a meaningful estimate for projection,” about three were not in effect, and cost projections weren’t published for three others for “confidentiality reasons.”

In their platform the Liberals committed to finding $3 billion in annual savings through tax expenditure reform. Last week, Morneau told the Globe and Mail he still sees that as a realistic target.

Two of those tax expenditures – the Children’s Fitness and Arts Tax Credits – will be eliminated in 2017 according to last week’s budget. The Children’s Fitness Tax Credit was not in effect in 2015.

If, further down the line, the government wanted to reduce the deficit further it always has the option to increase government revenue by directly raising taxes.

One option would be to raise the federal gas tax, which currently sits at 10 cents a litre.

Politically, an increase to the fuel tax might play better than an increase to the GST, given that gas prices are down substantially, said Kesselman.

“It is an effective revenue source in the sense that there’s a lot of gas being bought out there, so if you increase the federal tax by a few cents per litre there’s no question you will raise a bunch of revenue,” said Ragan.

But raising the GST be more efficient because it applies to everything not just one product, he said.

From a carbon pricing perspective, raising the gas tax isn’t the approach either, said Ragan.

“The problem with the federal excise tax on gas is that it only applies to gas, it doesn’t apply to all of the other sources of carbon emissions in the economy,” he said.

“I think it’s much more efficient and better for the economy to actually attach a carbon price to the widest possible collection of emissions you can, and a federal gas tax just doesn’t do that.”