Uber for Business account admins can require expense codes for trips taken on the business profile.
If your admin required expense codes, you'll be prompted to select an expense code from a list or enter your own before requesting a ride.
If you aren't prompted to but want to enter an expense code or memo, you can do so in the "Expense info" tab at the bottom of your screen after you've requested a ride.
NOTE: The expense memo must be filled out before the trip ends. You can't edit expense info after a trip is complete.
Expense codes will be noted in your monthly statement and trip receipts. Your company's admins also have access to this info in their dashboard. Ask your admin about your company's expense memo policy.