Uber and Lyft drivers have cruised the streets of San Francisco for years. But the city has now decided that drivers who work for more than seven days in a year need a business license. 

Nearly 37,000 people have been identified by the city as drivers for either Uber or Lyft, according to a press release issued on Friday by city treasurer José Cisneros

Cisneros did not say how the city came across a list of names, but the notice being sent to drivers comes from "two years of enforcement work, including multiple requests for information and subpoenas to get sufficient data about business operations" from companies like Lyft and Uber. 

Knowing that both Lyft and Uber have both actively fought having information released, it's likely the data wasn't passed over voluntarily. San Francisco was not listed as a city that had requested data in Uber's transparency report, although its airport has information about 44,000 drivers.

"Uber partners with entrepreneurial drivers and as independent contractors, they are responsible for following appropriate local requirements," an Uber spokesperson said. 

Lyft, on the other hand, was worried that forcing registration would compromise driver privacy.

"We have serious concerns with the City's plan to collect and display Lyft drivers' personal information in a publicly available database. 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 ridem" a Lyft spokesperson said.

Cisneros will start by sending out three batches of letters to the identified drivers over the coming days, according to the SF Chronicle. Each driver will need to register him or herself as a business within the next 30 days and pay a $91 annual registration fee and display the registration in the vehicle, or face additional fines. If each driver registers, that generates approximately an extra $3.37 million for the city's coffers.

While the city says it's taken two years of enforcement work to get here, the move to require business licenses is also a reflection of the legal battles that the two companies are involved in. 

Lyft has been trying to settle a court case which would dole out cash to some drivers, but consider them independent contractors in the end. Uber's case is still up in the air as to whether they are employees of the company or independent contractors. 

Now San Francisco is flipping the argument around on the ride-hailing companies arguing that if their drivers are truly independent contractors, then they need these business licenses to be able to operate in the city.

This story first appeared on Business Insider.