As empty storefronts plague San Francisco’s beloved neighborhood shopping districts, the Board of Supervisors is close to placing a tax on the March ballot that would try to curb such vacancies.

The measure, proposed by Supervisor Aaron Peskin, would hit landlords with an annual tax if their properties sit empty for six months — 182 days, to be exact — at a time. The point? Deter “bad actors” from intentionally keeping storefronts vacant for various reasons, including holding out for a tenant who can pay a higher rent.

“I want to be frank about our goal here,” Peskin said at Wednesday’s budget and finance committee meeting. “And that is to point fingers at a handful of bad actors. This will give the city the necessary tools to ... revitalize merchant corridors.”

But critics point out that some landlords are earnestly trying to fill space, but failing as more shopping moves online and as small businesses struggle to afford the high cost of doing business in San Francisco.

The measure — dubbed the vacancy tax — would levy a fee on landlords based on the length of their ground-floor storefront and how long it has been empty. The tax would begin at $250 per linear foot in year one, rise to $500 in year two and then double to $1,000 for each year thereafter.

Any proceeds generated from the tax would be donated to the Small Business Assistance Fund.

Landlords could apply for an exemption for various reasons, including if they have been hurt by a disaster or if they apply for permits to make improvements to the property.

Nearly every major neighborhood in San Francisco is peppered with vacant storefronts, from the Haight to North Beach to the Richmond. That’s because local retailers have been socked by increased costs of doing business, arduous permitting processes and dwindling foot traffic.

Empty stores can also hurt surrounding businesses by creating an eyesore in the neighborhood and also reducing shoppers in the area.

While Supervisor Rafael Mandelman said he supports the idea of the tax, he said he is worried how it could harm landlords whose storefronts are empty due to factors out of their control — like a dearth of tenants who can afford to operate a business in the city.

“We don’t have the ability to foresee every circumstance and understand ... how many of those property owners are negligent, versus how many of those are just stuck,” he said.

The budget and finance committee must vote on amendments to the measure at a special meeting on Monday. From there, it will likely move to the full Board of Supervisors on Tuesday. If the board approves the measure, it will head to the March 2020 ballot where it will need a two-thirds vote to become law.

If the tax passes, it would mark City Hall’s latest effort to make San Francisco commercial districts more vibrant.

— Trisha Thadani

Trisha Thadani is a San Francisco Chronicle staff writer. Email: tthadani@sfchronicle.com Twitter: @TrishaThadani