The lengthy Massachusetts budget process is set to officially begin with the filing by Governor Deval Patrick of his spending plan for the next fiscal year.

Patrick has already revealed several key aspects of the budget that will be sent to the Legislaturet today. He's seeking to hike the income tax rate from 5.25 percent to 6.25 percent, while lowering the sales tax from 6.25 percent to 4.5 percent. The net revenue increase would help fund transportation and education initiatives.

The exact level of proposed state spending for the fiscal year starting July 1 will be revealed in Patrick's budget request. The current budget exceeds $32 billion, but lower-than-expected tax collections recently prompted the governor to trim spending by $540 million.

Lawmakers are expected to spend several months reviewing the spending plan.