After verifying the customer's identity, the rep could look up and relay the policy number to the user.
The customer service rep has to read a long policy number over the phone, and the user has to listen and type that number into the form field.
Consider the situation where a user started filling out a claim form but could not locate their policy number.
B: Good. Put down your policy number on the form. I'll give you a receipt and you can get the money back. I think they reimburse almost 100%.
During this information relay there's a margin for error; the wrong data could end up in the policy number field.