If you previously submitted a reference letter for a grant applicant, and you now want to replace that letter with an updated or corrected letter, you can do so as long as:
The application deadline has not passed, and
You know the confirmation number from the submission of the first letter you submitted. When you submitted the letter initially, you saw a screen and received an email, both of which contained the submission confirmation number. Following is an example of the email with confirmation letter:
For letter requirements, see Requirements for Letters.
To submit an updated letter, which will replace the previous letter, follow the steps in Submitting Reference Letters, making sure you enter all the same information for the applicant (last name, Commons ID, FOA) that you entered the first time you submitted. Additionally, you must enter the confirmation number that you received after your first submission in the Reference Letter Confirmation # field.