Opposition parties will get their first opportunity to assess the true state of the public finances when Department of Finance officials open the books to them today.
Fine Gael and Labour will receive a detailed briefing on the expected tax take and economic growth forecast for the year ahead.
The Taoiseach Brian Cowen is planning to meet the main opposition leaders about the Budget later this week.
Yesterday, the Taoiseach warned that those forecasts are lower than previously thought - meaning tougher Budgets next year and into the future.
The briefings will serve as a precursor to a meeting expected to take place later this week between the Taoiseach and the leaders of Fine Gael and Labour Enda Kenny and Eamon Gilmore.
Both opposition parties will then be under pressure to produce their own alternative budget plans or to agree a consensus with the Government.