Chartered Accountant
687 Points
Joined August 2018
If you have included those b2b invoices earlier in GSTR-3B and only missed to disclose the same in GSTR-1, then you can add the same in July'18 GSTR-1 by mentioning the actual date of invoice. No interest is applicable.
However, if it was missed to disclosed both in GSTR-1 and GSTR-3B then you will have to pay interest @ 18% p.a and disclose the same in July'18 GSTR-3B and GSTR-1.