Return under GST

On filing the GSTR 3, if actual liabilities are different from those declared in GSTR 3B, the system will update the (difference) between GSTR 3B and GSTR 3 automatically. In case, actual liabilities in GSTR-3 are higher than those declared and paid with GSTR-3B, you will have to pay the extra amount tax along with interest on the extra amount.

GSTR-3 is a monthly GST Return. It contained two parts i.e.Part A, Part B while GSTR-3B is the return form a taxpayer needs to file separate for each GSTIN. However, one don’t have to fill invoice level of information in this form just the total values for each field. All normal registered taxpayers should mandatorily file Form GSTR-3B.

good clarification and information