GST - Whether Credit and Debit Note needs to be given?

Generally , for corrections involving changes in taxable vaue or tax amonts, a debit/credit note might be required depending on the nature of the correction and its impact on the recepient. However, in this case, since the total invoice value is the same and you're correcting the taxable value for accurate reporting without changing the tax amount paid or impacting the recipient's tax, making the correction in the amendments tab should suffice without needing a debit/credit note. 

Impact on GSTR-3B: When you file GSTR-3B for the month, the correction made in the amendments tab for the invoce in question will reflect in your GST return. Since the total tax liability is n't changing (CGST +SGST on Rs.18,011 = Rs.1,621+Rs.1,621, and no tax on the difference because total value matches), the impact on 3B filing this month regarding tax liability is nil. The correction ensures accurate reporting of taxable value. 

The tax liability does change --> The invoice is supposed to be nil-rated (Rs. 21,253) and it was incorrectly split into Rs 18,011 with 18% tax (Rs 1,621 each CGST, SGST) totalling to original value of Rs 21,253. If invoice is amended, wouldn't the credit given to purchaser reduce?