Vacant storefronts mar nearly every shopping district in San Francisco — from North Beach to Union Street. More than just eyesores in the city’s beloved shopping districts, empty retail spaces are lost opportunities for tax revenue, jobs and foot traffic that help support neighboring businesses.

Now the Board of Supervisors has a plan to help: a tax on landlords who leave their storefronts empty for more than six months. The point? Encourage building owners to quickly rent out spaces, by either settling for a lower rent or finding a pop-up or short-term tenant.

But critics worry how the tax will hobble landlords whose storefronts are vacant for reasons out of their control — like the city’s arduous permitting processes and the high cost of doing business in San Francisco.

The supervisors will vote on the proposed March ballot measure — dubbed “the vacancy tax” — at a special board meeting Thursday. They will likely pass it to voters. It would need two-thirds approval at the ballot to become law.

“This is a long overdue common-sense policy that is not about raising any funds,” said Supervisor Aaron Peskin, author of the measure. “It’s about changing certain bad actor landlords’ behavior, and creating a disincentive for long-term vacancies.”

Peskin and supporters of the tax say it will target landlords who intentionally keep their properties vacant while they hold out for higher rent. But several landlords and small business owners interviewed by The Chronicle criticized the idea, saying it will penalize good landlords along with the bad and won’t help with retail’s underlying woes.

“We’re hustling like crazy so that we can fill our retail vacancies around the city,” said Clinton Textor, a local real estate investor and broker. Textor said he has seven properties that he either owns or leases in the city, two of which are vacant — one on Union Street and the other on Valencia Street.

“You can’t make us more motivated to fill that space than we already are,” he said.

Textor’s empty storefront on Valencia Street is also hurting his neighbor, Jonah Buffa, who owns Fellow Barber next door. Buffa said the boarded-up storefront adds blight to the area and even attracted squatters this summer.

“It was terrible for me,” he said. While Buffa said there needs to be a more targeted measure in outing bad landlords, he said the city also needs to make it easier for small businesses to operate in the city.

“What we don’t want is something that makes it even more difficult for small businesses to survive,” he said.

Empty storefronts are a pernicious problem all over San Francisco. While people commonly blame the rise of online shopping and dwindling foot traffic for the industry’s woes, a Chronicle investigation into the shuttered sites showed landlords and small businesses are also impacted by the high cost of labor, rent and a city permitting process that can take up to a year and a half.

The proposed measure 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, increase to $500 in year two and then double to $1,000 for each year after that. It would apply only to the city’s 30 or so neighborhood commercial corridors, like those in North Beach and the Haight and on Ocean Avenue.

If it passes, it would go into effect in January 2021.

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.

The city controller estimates that the tax will generate roughly $300,000 to $5 million annually. But Peskin said the goal of the tax is not to collect revenue — but instead spur landlords to lease their properties faster.

“This is an avoidable tax that we do not want to collect,” he said.

Money from the tax will be donated to a Small Business Assistance Fund, which would be created by the measure.

While a tax could encourage landlords acting in bad faith to rent out their spaces, Textor says he doesn’t know what else he can do to rent his spaces out faster. He’s been working with the city for months to get construction permits to fix up his spaces so a tenant can move in.

Textor likely wouldn’t be subject to the tax — the measure exempts those who apply for and obtain permits from the city — but he still feels the idea is “misguided.”

“I don’t know if you’re going to get anyone to do anything,” he said. “I can’t get behind the idea that a tax is somehow going to motivate someone with a big space to lease it out. They are already forgoing the income, which is way more important and impactful than the tax would ever be.”

But Elias Bikahi, owner of Caffe Sapore, said a vacancy tax could give small business owners like him some bargaining power when it comes to how much rent they are asked to pay.

Operating his North Beach cafe has become harder and harder as his profits have been squeezed: he said his rent has nearly quadrupled since he opened in 1993. Fewer people in the city are leaving their offices for lunch. And labor has become more expensive, as minimum wage has increased and the housing crisis has increased the city’s cost of living.

Even though his space is becoming unaffordable, all the vacant spaces in North Beach are too pricey for him, too.

“The owners and landlords can just do whatever they want,” said Bikahi, who has known Peskin since the ’80s. “They should have some rule and laws regarding that, and I think taxing them for vacancies is one part of that.”

If the tax passes, it would mark City Hall’s latest effort to make San Francisco commercial districts more vibrant. Over the past year, there have been other efforts, such as imposing an annual fee on building owners who don’t register their vacancies with the city, and streamlining the permitting process for small businesses. Peskin is also working on legislation that would curtail small business fees.

It would also make San Francisco part of a growing wave of cities around the country trying to stem the glut of retail vacancies. Arlington, Mass., passed a vacant storefront fee in 2017, and New York City and Boston are considering similar efforts.

“I hope this legislation will bring the prices down, and also be an incentive for people to keep their tenants,” said Supervisor Sandra Lee Fewer, who supports the tax.

Supervisors Hillary Ronen, Matt Haney, Vallie Brown, Shamann Walton, Gordon Mar and Rafael Mandelman also said they support the tax.

Though originally skeptical of the measure, the Office of Small Business now supports the measure after Peskin made a number of amendments to protect tenants from having to shoulder the burden of the tax. For example, one amendment will prohibit landlords from passing the cost of the tax onto a tenant by raising its rent after it goes out of business, but hasn’t reached the end of its lease.

“There is a consensus that we need to take some action against these problem owners,” said Regina Dick-Endrizzi, executive director of the office. But, she said, the office will “monitor” the tax to make sure it is not inadvertently harming landlords who are trying to lease their businesses as soon as possible.

Ben Bleiman, co-owner of Tonic Nightlife Group, operator of three bars — Tonic, Teeth and Soda Popinski’s — similarly commends Supervisor Peskin for “doing something” about the vacancy issues.

But Bleiman, who is a former landlord, said it’s unfair to charge the tax when the city is mainly responsible for businesses taking an unreasonably long time to open. He organized dozens of small business owners to rally at a recent Small Business Commission meeting to advocate for more help from City Hall in dealing with San Francisco’s crushing cost of doing business.

“The process of opening a small business is so onerous in this city and with high commercial rents, labor costs, it’s too much for small businesses,” he said.

Trisha Thadani and Shwanika Narayan are San Francisco Chronicle staff writers. Email: tthadani@sfchronicle.com, shwanika.narayan@sfchronicle.com Twitter: @TrishaThadani, @Shwanika