The Central Bank has said the final bill for Anglo Irish Bank means another €5bn is needed from the taxpayer, bringing the total to €29.3bn.
However a further €5bn again could be needed in a worst case scenario set out by the bank this morning.
Effective nationalisation of AIB is also to take place.
The Central Bank says once Anglo is split into an asset recovery bank and depositors bank the capital required from the taxpayer is €5bn.
This brings the 'final' bill to €29.3bn, but the bank said losses under a severe hypothetical scenario could be another €5bn.
The worst-case scenario assessment brings the possible final tally close to the €35bn estimate from ratings agency Standard and Poors.
"The assessment we have published today of the costs of Anglo’s restructuring reflect careful analysis of information from a range of sources," said Financial Regulator Matthew Elderfield.
" It also includes a projection based on a prudent hypothetical stress scenario which gives guidance as to the likely upper bound of those costs."
Meanwhile the Government is to pump another €3bn into AIB after the bank suffered a greater than expected haircut on NAMA loans.
The Government is also to shortly announce that less loans from AIB and Bank of Ireland are to go to NAMA - up to now anything over €5m qualified - but this will increase to €20m.
Meanwhile it has also been announced that changes are on the way in AIB management.
Group Managing Director Colm Doherty has had his contract terminated and is to leave the bank before the end of the year.
Dan O'Connor is to step down as executive chairman in the coming weeks.
Finance Minister Brian Lenihan said he hoped the actions announced this morning will give confidence to markets.
In a statement this morning Minister Lenihan said it was "an urgent and immediate priority to reinforce international market confidence in our ability and commitment to restore our banking system to health'.
The Government is now expecting a very substantial spike in Ireland's general government deficit this year, as a result of the support for the banks - bringing it to almost 32% of GDP.
Minister Lenihan confirmed this morning that a four-year budgetary plan, incorporating the plans to meet European requirements on reducing that deficit, will be published in early November.
Opposition parties criticised the Government's handling of the entire Anglo bailout.
Labour's deputy leader, Joan Burton, described today's announcement as Irelands "black Thursday".