regarding late fees of gstr 4

The due date for filing of GSTR-4 for quarter ended December 2017 was 18th January 2019.
Further late fee for filing of GSTR-4 as per notification 73/2017 is
I) if it is "not a nil return" - Rs 25 everyday during which the failure continues
II) if it is a "nil return" - Rs 10 everyday during which the failure continues
The above limits are subject to maximum of Rs 5000

The late fee mentioned in the supra is under CGST Act,2017 only. Similarly the same late fee is applicable under SGST Act also.

Hence the total late fee during the failure of filing GSTR-4 is
I) if it is "not a nil return" - Rs 50 everyday
II) if it is a "nil return" - Rs 20 everyday.

interest also should be paid with late fees.