The Government now believes it will take in €2.2bn more in tax revenues than it expected at the start of the year.
Estimates of Receipts and Expenditures, published this morning, show the Government is spending an extra €1.5bn this year through supplementary estimates, which will raise the spending level in next year's budget as well.
The eve of the budget white paper shows most of the extra revenue coming in the form of corporation tax, which is expected to yield €1.5bn of the €2bn in additional revenue for this year.
The white paper implies that €1.5bn of that extra money will be spent in this year's budget, by way of supplementary estimates, mostly for health and social protection.
This additional spending would result in a general government deficit of 2.1% of GDP, still ahead of the deficit target of 2.3% set in the spring statement. The remaining excess tax will be used to pay down debt.
Forecast economic growth of just over 4% next year would result in a budget deficit of 0.8% in 2016.
However, that is before changes in next week's budget, which will increase spending and cut taxes by a combined €1.5bn, suggesting a Budget Day deficit target of around 1.3-1.4%.
The white paper also includes an expected receipt of €1.6bn from the sale of Contingent Capital Notes, a repayment of part of the State's investment as part of the bank bailout.
The figures in the white paper are prepared on a technical pre-budget basis, and do not include any new policy measures to be announced as part of the 2016 Estimates and Budgetary process.
It also provides for about €40m in election expenditure in next year's State budget, but this money can be spent this year if necessary.
Fianna Fáil chooses director of elections
Meanwhile, Fianna Fáil leader Micheál Martin has told his annual Cáirde Fáil dinner that former minister and TD Pat Carey is to be the party's director of elections for the General Election.
Speaking to supporters in Dublin tonight Mr Martin accused the coalition of delaying the recovery by policies that favoured the better off.
He also claimed the extra funds identified ahead of Tuesday's Budget would be used to bribe the electorate in the run-up to Christmas.