Before submission or travel, not after. A correction requested while the employer still has the file open takes far less effort than explaining a discrepancy that has already been presented.
Fix it while the file is still internal
Give the employer a specific deadline tied to the intended filing or travel date, and hold that date rather than proceeding with a letter you expect to correct later. If human resources cannot turn a corrected letter around in time, moving the date is usually the better trade. A document already in a reviewer's hands cannot be quietly swapped.
Request the transcript and registrar letter as the first step, then use the waiting period to assemble employer documentation and confirm the profession's credential requirement. Confusion usually starts with an offer letter that recites a multi-year engagement, which reads to the applicant like a guarantee of a matching admission. A professional order may take weeks to issue a confirmation of standing, a university transcript request has its own queue, and a U.S. employer's legal department may revise the letter several times. Work backward from the last fact that could change the classification: finalized duties, a required credential record, the employer letter, or a changed client assignment.