What counts as filing date for I-751?

[hopefulandhappy]

I dropped off my form + documents at Fedex and the expected delivery date is Sept 1.

How do you distinguish the filing date? Is it the date you mailed out your application, the date USCIS received it or the date they issue the 797C receipt?

[brightarmyruler]

I dropped off my form + documents at Fedex and the expected delivery date is Sept 1.

How do you distinguish the filing date? Is it the date you mailed out your application, the date USCIS received it or the date they issue the 797C receipt?

In my case I sent my application March 18 and they received it March 19th however my 90 days filing should be March 20th. Since the received date (UPS delivered it March 19th) was one day ahead of my 90 days filing, I got a rejection in April 24th stating I filed my application prior to 90 days. Documents returned on April 28th and the scanned date by USCIS was April 8th.