Rick Steve's advises its Bularia tour participants regarding the use of Taxis from the Sofia Airport. There is an official Sofia Airport sanctioned provider "Yellow Cab" you want to use. Very important. There are unabashed scammer handlers operating in the arrival halls that will claim to be from the Yellow Cab company and direct you to a scammer cab. They will tell you its the Yellow Can company(yes the cab might be yellow but its not the legit company). Don't trust anyone who approaches you no matter how exhausted you might be from your flights. The scammers will claim to be an official cab, indicate they are metered but the meters can be loaded with jibberish multipliers or obscured so you cant see the meter from the back seat. The result can be a significant overcharge vs the official provider. This is the RS verbiage as of May 2026.
"Do not accept a taxi ride from anyone who approaches you in the arrivals hall. Instead, go directly to Yellow Taxi (look for the yellow “TAXI” signs). Unofficial cab company CK Taxi Cabs is known to scam tourists, so only take cabs from the Yellow Taxi desk. At the counter, tell them you want to go to the (wherever you are going). They’ll give you a reservation form with a specific cab number and call it for you. Wait at the desk so they can point out your cab when it arrives. If the kiosk is closed, leave the arrivals hall through the exit to your right. You’ll see a line of official Yellow Taxi cabs. Before placing your luggage in the taxi, we strongly recommend that you crosscheck the cab number with the number on your printed reservation form."
Again, Yellow Taxi is the official Taxi provider for the airport. Here is the link to their website so you can see the logo.
As the instructions indicate, the main kiosk might be closed and the scammers will hover and act like they are returning to the desk after stepping away, its a ruse. Exit to the right ! Additionally, they are all over the city proper as well and have there own app (I have not used). Once you are in Sofia, many of the hotels have a Yellow Cab company call button/terminal in their lobbies such as did the Arte Hotel on our recent visit. Very convenient.
Good luck, Bulgaria is a great place to visit.