https://community.expensify.com/discussion/48166/united-cancellatio...
United’s flight cancellation policy includes:

24-Hour Cancellation: You can cancel most flights within 24 hours of booking for a full refund.
Airline Policies:
After 24 hours, cancellations are subject to the 888-829-1467airline's policies,
which may include fees or provide travel credits instead of refunds.