She said the Stormont Executive was going to set a one-year budget.
This was because it would be wrong to "tie the hands" of new ministers who might want to set fresh priorities after the Stormont elections, she said.
Mrs Foster said there was now a clear picture of Stormont's finances after the comprehensive spending review.
She told MLAs during Question Time in the assembly that she expects day-to-day departmental spending to be reduced by 5% in real terms by 2019/20.
But she also anticipates spending on infrastructure projects to rise by 12% in real terms by 2020/21.
The finance minister said she would be discussing the budget with other ministers before Christmas.
Mrs Foster said: "Colleagues will have to look at efficiency savings again in 2016/17."
In response to a question from Sinn FÃ©in MLA Daithi McKay, Mrs Foster welcomed the Chancellor's decision not to proceed with cuts to tax credits.
She said she was looking forward to having discussions in the executive about what to do with Â£240m which was set aside in the recent Fresh Start Agreement to lessen the impact of tax credit cuts in Northern Ireland.
Finance Minister Arlene Foster has told MLAs she hopes to have a budget for the next financial year in place by the end of January.