GSTR 3B Missing invoice

Taxpyer is a railway contractor filed 10 invoice in GSTR 1 in Apr month but one invoice of Rs.1.2Cr was not declared in gstr 3b because it was not clear that the invoice will be accepted in same month by the railway or not. Subsequently invoice was accepted by them in same month.

Now as invoice was already uploaded in R1 of April but tax is paid in the 3B of May 23. Whether Interest liability would be @ 18% and penalty will be imposed or not.