Lyft and Uber drivers in San Francisco that work at least seven or more days a year must now obtain a business license to come into compliance with city regulations.

As the San Francisco Chronicle correctly points out, Lyft and Uber drivers have been operating in the city for years. Why drivers are just now being asked to obtain a business license isn’t entirely clear. City Treasurer Jose Cisneros did tell the publication, however, that one reason for the change has to do with the fact that the city launched its online business registration system just last month.

Prior to March, those interested in registering for a business license had to do so in person at City Hall.

Another likely reason the treasurer is just now taking action is the fact that he now has a list of Lyft and Uber drivers. When questioned on the matter, Cisneros would not say how he came into possession of the list which is comprised of 37,018 drivers. Both Lyft and Uber have long refused to provide the data to the city.

A business license in San Francisco is priced at $91 per year for those that collect less than $100,000 a year in fares. Assuming that every driver paid for a business license this year, the city would receive more than $3.37 million in revenue.

What’s more, drivers that met the criteria for needing a business license in previous years must back pay those fees, too.

Cisneros is in the process of mailing out letters to those he has identified as drivers for the two ride-hailing services. Recipients have 30 days to obtain a license; failure to do so may result in penalties and payment obligations, the letter states.