H1B--->B2 COS Legal Stay

USA B1/ B2 Visitor Visa
1

I am currently on my grace period, and my B2 Change of Status (COS) application was filed before it is to end. However, I have not yet received the receipt number.

Can I legally stay in the U.S. without the receipt number? My application has already been delivered to USCIS.

Since I have only one week left, is there a way to find out the receipt number before waiting for the mail?

2

If USCIS have received the mail while you are still in the grace period, you should wait till you receive the receipt. Though if the change of status is not approved within 6 months from the end of your grace period, Ibwould advice leaving the US at that point.