In general late fees 50 per day or If Nil GSTR-1 than 20/- per day but Currently, in practice, the late fee is often not imposed strictly on delayed GSTR-1 filings.
(Still dept not follow the late fee against GSTR 1. Also in this situation Buyers in trouble for claiming ITC in the same invoiced month. And Seller get presure from buyer.
So, in this matter GSTR 1 late filing related activities discusses between seller and buyer.)