The monthslong process of constructing a more than $40 billion state budget is about to begin in earnest on Beacon Hill.

Republican Gov. Charlie Baker on Wednesday will unveil his spending plan for the next fiscal year.

Baker and the Democratic-controlled Legislature have agreed to base their spending assumptions on a forecast of 3.5 percent growth in tax revenue.

The governor and House Speaker Robert DeLeo have ruled out major new taxes. But there is uncertainty as to how voters will respond to prospective November ballot questions, one calling for a surcharge on the state's highest earners, and another that would trim the sales tax.

The next fiscal year is also likely to be the first the state collects revenue from resort casino gambling and the sale of recreational marijuana