C. Scott Clark is a former federal deputy minister of finance, and Peter DeVries is a former federal director of fiscal policy.

It's been a few weeks since the federal Liberals' first budget. Traditionally, a government's first budget is a political document that focuses on fulfilling election promises. Given this political nature, the Prime Minister's Office is naturally very involved in its preparation. The objective is to get the budget over with and off the front pages quickly. But unfortunately for Prime Minister Justin Trudeau and Finance Minister Bill Morneau, their first budget is still in the news, and not in a favourable way.

This budget remains in the news not because it failed to deliver on political promises, but because it failed the government's election commitment to create "a planning framework that is realistic, sustainable, prudent and transparent." Its greatest failure was lack of transparency.

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One of the most important rules in budget preparation is that budget documents should contain as much information and explanation as possible. Too little will only create problems. Putting the fiscal analysis in an annex may have appeared unimportant, but it was a big mistake. It downgraded the importance of the fiscal numbers and suggested that the Finance Minister did not believe the fiscal numbers were all that important.

But fiscal numbers are the most important part of any budget – ask anyone who has ever been in a budget lockup. Last week, the Parliamentary Budget Officer released a report criticizing the government for "making changes to the presentation of its fiscal plan that have made it more difficult for parliamentarians to scrutinize public finances."

In particular, the budget did not provide a detailed reconciliation of changes resulting from economic developments and policy initiatives since November's fiscal update. Past budgets always included detailed reconciliations with five-year projections for major policy aggregates.

In response to a PBO request for this information, the Finance Department provided the data, but indicated that it was confidential and could not be made public. This restriction was removed last Friday. After reviewing the data, it is hard to understand why the Finance Department did not include it in the budget in the first place. There was certainly no reason to classify it as confidential. The first lesson for the Finance Minister for his next budget is to provide a fiscal plan that includes as much information and explanation as possible.

His second lesson is not to include an excessive level of prudence and to be transparent about how the prudence reserve is to be used. Obviously, a budget should include a reasonable amount of insurance to guard against forecasting errors and unforeseen events. But the amount of prudence in this budget was well over the top.

Nominal gross domestic product was reduced by $40-billion annually, resulting in a reduction in revenue of about $6-billion beginning in 2016-17. According to the PBO, only once between 1994 and 2014 did the private sector forecast overpredict nominal GDP by more than $40-billion, and this was during the 2009 financial crisis. In past budgets, prudence was usually set at $3-billion a year. Too much of it has resulted in a deficit forecast based on unrealistic economic assumptions that no one believes.

It would also be more transparent if the prudence reserve was shown as a separate line item in the budget, and not applied to a reduction in nominal GDP and reduced revenue components. Providing detailed revenue forecasts based on unrealistic economic assumptions makes no sense. Instead, detailed revenue forecasts should be based on the average private-sector economic forecast, with the prudence shown afterward as a separate line item in deriving the final budgetary balance.

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A third lesson for the next budget is that the government should be transparent about what the prudence is to be used for. Previous governments, Liberal and Conservative, stated that the prudence or contingency reserve could not be used to finance new policy initiatives. If not needed, it had to be used to reduce the deficit and debt. To date, the Finance Minister has been silent on this issue, suggesting that the "prudence" will be used for new spending. If so, then the government should state clearly that it is including the reserve for future spending initiatives.

A fourth lesson for the next budget concerns transparency and fiscal anchors. There has been criticism of the budget over the government's failure to fulfill its election promises to keep the deficit below $10-billion and to eliminate the deficit in three years. But the government had already addressed these criticisms in releasing a February fiscal update. There were also criticisms over the failure to fulfill some election promises, but this was to be expected as well.

Nevertheless, the government should accept fiscal reality: The deficit will not be eliminated in the foreseeable future. Right now, the government's challenge is to ensure a declining debt-to-GDP ratio, which won't be easy given the long list of costly election promises that were not included in its first budget. In addition, the next budget or fall update should include long-term fiscal-sustainability analysis. This will allow financial analysts to assess the impact of the new policy initiatives on the sustainability of government finances.

Perhaps the most important lesson for 2017 is that the Prime Minister should give the Minister of Finance and the Finance Department the responsibility and accountability for preparing the budget. In our experience (a combined 30 budgets), the odds of a budget's success are inversely related to the number of people involved in its preparation. Learning this lesson would go a long way toward ensuring that the other four lessons are learned, too.