Do you need a car seat in a taxi USA?

Yes, you do require car seats in taxis in USA. It's unsafe and illegal for parents to have their kids in taxis without car seats. 

As of October 2023, all states and territories in the United States have laws that require child safety seats for infants and children based on specific criteria, including age, weight, and height. These requirements typically apply to privately owned vehicles, taxis, airport shuttles, rideshare services. 

In all states, the same child safety seat requirements that apply to private vehicles also apply to taxis. This means that children would need to be secured in an appropriate child safety seat while riding in a taxi, depending on their age, weight, and height. The three stages you mentioned—rear-facing, forward-facing (harnessed) seats, and booster seats—are part of these requirements.

It's important to note that some states may have specific requirements in their laws regarding child safety seats in taxis. Local regulations and ordinances can also come into play, so it's essential to check the current laws and regulations in your specific state and locality to understand the requirements for child safety seats in taxis. Laws can change over time, so it's crucial to stay up-to-date with the latest regulations.