For on-paper names where it counts, strive for exact alignment of names among:
SSN
Passport
TSA Pre-Check and airline loyalty programs
Driver’s license
IRS tax returns
Credit card accounts
Bank accounts and debit cards
Insurance policies and named beneficiary documents
Future headaches will be avoided if this can all be aligned now.
Military records, military pay accounts, future security clearance and initial CAC (Common Access Card, military ID) will be created based on supporting documents supplied by the incoming plebe or cadet. This is typically a birth certificate which, if the name is changed, will have to be augmented by supporting documents.
Assume each SA has its own internal database, and the legal name would have to be inputted there.
Once the foundation is laid for the legal name for various official name items, it’s generally okay to use a preferred first name for informal reasons. Signing documents or submitting a term paper, say, with a variation on the surname, might cause difficulty.
We had a USNA sponsor son with a lengthy hyphenated last name and a first name which didn’t lend itself to a shortened version. He was AAAAAA MI BBBBBBB-CCCCCC. Among the mids, he was “hey, CCCCCC.” His USNA name tag and of course CAC and all other official systems had the full name. Once out in the fleet, his flight suit name tag read “LT BBBBBBB,” but of course his orders, fitness reports and other official documents had the full name. He always submitted written work and signed official documents with his legal name.
Best to get going on that now if it is going to be done. If an appointment is in hand, the floodgates will soon open for all the forms to be completed for various things. Admissions will have to be informed of any changes as soon as they are final, so the internal database can be updated as to the name associated with the SSN identifier.