Attention, Uber and Lyft drivers! San Francisco wants to rake in money from you.

On Friday, the treasurer for the City and County of San Francisco announced that he had begun mailing out business registration notices to the "nearly 37,000" people who drive for "Transportation Network Companies," the formal name in California for such on-demand companies.

The city says that these drivers are required to pay an annual business registration fee of $91 per year for operating a business in the city—which includes being a driver for a company like Uber or Lyft. Assuming full compliance, the new fee collection would result in new annual revenue of over $3.3 million per year.

There has been a pitched battle as to whether such drivers should be considered as employees (where they would be subject to various benefits paid for by their companies) rather than contractors. In the case of Uber, a class-action lawsuit continues to move through the courts, with a trial date set for later this year.

"I take seriously my obligation to fairly implement San Francisco’s business registration requirements," Treasurer José Cisneros said in a statement. "I urge all the people receiving this notice and all unregistered businesses operating in San Francisco to take prompt action to come into compliance immediately."

In a statement, Uber spokeswoman Laura Zapata told Ars that drivers are "responsible for following appropriate local requirements." For its part, Lyft took a harsher tone.

"We have serious concerns with the City's plan to collect and display Lyft drivers' personal information in a publicly available database," spokeswoman Chelsea Wilson said in a statement. "People in San Francisco, who are choosing to drive with Lyft to help make ends meet, shouldn't have to compromise their privacy in order to share a ride."

Wilson did not respond to Ars' question as to how these "concerns" would be expressed.

105,000 registered businesses

The Office of the Treasurer re-iterated to Ars that registering is required of anyone engaging in business in the city, whether they are a freelance journalist, a street musician, or self-employed Web designer. However, it is unlikely that such large swaths of people are normally targeted at one time. If businesses do not register, they are subject to enforcement by the city.

"We have a number of enforcement tools available to us—penalties and interest for past due registration periods is the most common," Amanda Kahn Fried, a policy and legislative manager, told Ars.

Fried did not explain how the city came to acquire the names and contact details of all of these drivers.

According to Cisneros’ office, "San Francisco has over 105,000 registered businesses, which pay $1.2 billion per year to the Treasurer’s Office in business taxes. Businesses can be registered online at http://sftreasurer.org/registration.

Ars has contacted city treasurers in Oakland, San Jose, Portland, Seattle, Austin, and Chicago as to whether they would be implementing a similar policy. We will update this story when we hear back.