Twitter has told San Francisco officials that they plan to lease offices in the city’s Mid-Market neighborhood, but only if the Board of Supervisors approves a payroll tax exemption plan.

The exemption proposal could be voted on as early as the end of March.

In a letter to San Francisco Mayor Ed Lee, Board of Supervisors President David Chiu and San Francisco Supervisor Jane Kim, Twitter officials confirmed their tentative plans to move to the San Francisco Mart building on the southwest corner of Market and Ninth streets.

The social media company estimated that the cost of staying in San Francisco would cost them more than $30 million over five years in rent, taxes and other expenses. Twitter has considered moving down the Peninsula to a city that has no payroll taxes.

San Francisco levies payroll taxes on all companies with payrolls above $250,000.

At a budget and finance subcommittee hearing this week, dozens of people spoke out in favor of and against the proposal.

Twitter is currently based in an office in the South of Market neighborhood.