PennyandDanny

They really should upload an example letter for this situation to the example form section on VJ since it comes up a lot.
 
You just need to write a basic letter in a semi-formal format.
 
USCIS
address
 
RE- LPRS name,
A#
NOA case number
DOB
resident since date
address
phone number
 
date of letter
 
Request to switch to a divorce waiver
 
To whom it may concern:
 
On X date, I, (name), A# filed a joint petition with my spouse (their name) with the X service center (where you mailed it). My case number is X. (from your NOA).  On X date (spouses name) and I legally separated/physically separated/filed for divorce/divorced. Please accept this letter as my request to switch to a divorce waiver. I am/am not attaching the divorce decree. (if you are list date of divorce and court name/if not state it will provided when the court issues it.) I am also attaching X Y and Z for your consideration.
 
Signed
dated
(you can get it notarized but it doesnt have to be)
 
 
Keep a copy for your records and mail it with a tracking number to the same service center you sent the original ROC packet to.
 
Personally I would submit a short basic letter like the above and attach a longer affidavit about the relationship and its breakdown. That statement can be multiple pages long and refer to evidence that you attach. Think 'courthouse' style evidence. You can label the attachments as attachment A, B, C etc and refer to them in your affidavit. Example we had joint bank accounts at X bank (see attachment A) blah blah. We took a trip together to Hawaii (see attachment B-D) etc.,