One of the biggest Oregon political stories of 2016 will be the battle between business and labor over a proposed gross receipts tax aimed at the November ballot.

The measure, backed by Our Oregon, is designed to raised $2.5 billion a year by taxing corporations with Oregon sales over $25 million annually.

Our Oregon, a 501(c)(4) nonprofit that gets much of its funding from public employee unions, made small in-kind contributions to related political action committees working on tax increase measures over the course 2015, totaling $150,000.

Meanwhile, the business-backed group formed to counteract Our Oregon, called Grow Oregon, is going on the offensive.

Over the weekend, the political action committee of Associated Oregon Industries, historically the lobbying arm of big business, contributed $50,000 to a Grow Oregon affiliate called Grow Oregon Now.

Grow Oregon Now has begun canvassing businesses and chambers of commerce around the state in an effort to build opposition to the tax hikes.