In the past, when a petitioner filed an application for permanent residency and failed to include a required form or document that is listed in the USCIS instructions, they would routinely send a request for evidence and then allow 87 days to comply with the request. Should the request not be adequately responded to, USCIS would then issue a letter of denial for the application.
On July 13, 2018, USCIS generated new regulations that now allows it to circumvent the “request for evidence” process in many cases, and simply deny an application as a result of failing to include a required form or document in the original submission of an application package. The regulation went in to effect on September 1, 2018. Once an application is denied for this reason, there is no option for appeal, and the filing fee is not refunded. If the applicant is currently out of status, the denial letter will also instruct him or her to leave the country. The only course of action at that point would be to re-file the application and pay another filing fee.
Consequently, there is potentially no more “room for error” in visa and green card applications.
You can read the entire policy memorandum here:
https://www.uscis.gov/sites/default/files/USCIS/Laws/Memoranda/AFM_10_Standards_for_RFEs_and_NOIDs_FINAL2.pdf
Please be sure to obtain competent legal guidance for all your family immigration matters to avoid unnecessary denials, delays and expense.