Hi,

For 2021 and later:

-T3 Return electronic filing is E-filing: a CRA issued e-file number and password are required

- T3 Slip filing is XML transfer, requiring a transmitter number, Business/ Trust account number and matching Web Access Code, (WAC). All three of these are issued by CRA.

Entries for business number and WAC entered in Efile > Options do not populate the CRA XML server log in screen. Manual entry is required

More information can be found in a ProFile Community article here