After an agency adds certification request flags, is the agency allowed to make changes to that year's raw data record(s)?

If an agency has entered certification flags and they change any of the raw data it will reset the flag to an "M" flag.  This is whether or not they have submitted a certification letter to EPA.  An "M" flag basically signifies that something has changed since the agency has entered their certification flags.  If the change is before the submittal letter, they can then change the flags and then submit the letter.  If it is after a certification letter to EPA, then they will need to change the flag and submit a recertification letter/package.  However, if data (especially large amounts of data) is being changed, they should keep their Regional Office notified of needed changes and why.  The Regional Office can help them determine the best approach.