According to King County, one needs to apply for a business license if "You sell a product or provide a service that is taxable." So, dog sitting fall under this category?
OK. I just called Rover, which is located out of Seattle. They told me that since we are considered individual contractors, we don't need a business license, and that Rover does not take taxes out of your earnings. So we would not fall under this "taxable service" criteria. He said some sitters get a license just to be on the safe side. This is for King County. To be on the safe side, I also called the Washington Department of Revenue, who said the same thing. A business license on a state level is not necessary if you don't meet any of the criteria; however, you would need to check with the town/city you live in if a town/city license is required.
Every Rover sitter needs to check with their local zoning departments to see what the requirements are for operating a pet care business, more important if you board clients dogs in your home.
You do pay taxes on your income so I would guess your business qualifies as needing a license. Just because Rover doesn't deduct taxes doesn't mean you aren't liable for taxes. Caveat: I am in Texas. I would definitely call your local government to be sure.
Thank you for your comment. I contacted the Washington Department of Revenue and Rover both (also located in Seattle); both informed me a license was not necessary. If Rover deducted taxes, then I would need one, they said. :-)