A registrar for the court says the decision is to be posted online Friday at noon.
The Saskatchewan Party government took Ottawa to court over the carbon levy and the Appeal Court heard two days of hearings in February.
Saskatchewan is one of four provinces that became subject to the federal tax April 1 and the first to challenge it in court.
The province argued the tax is not constitutional because it is not evenly applied across all jurisdictions.
A lawyer for the Attorney General of Canada suggested Ottawa does have the power to impose a price on carbon because greenhouse gas emissions are a national concern.
WATCH BELOW: Coverage in Saskatchewan of the carbon tax