Debit Note Calculator
Work out the extra tax when you issue a debit note for under-billing.
Or enter the agreed percentage being returned / under-billed.
Enter the original taxable value and adjustment percentage to compute the note.
How the calculation works
Under-billed? A debit note increases the originally reported taxable value and tax so the paperwork catches up with what was actually owed.
- Adjustment
Original taxable value × Debit % ÷ 100 - Revised taxable value
Original + Adjustment - Additional tax
Adjustment × Rate ÷ 100
Worked example
You billed ₹80,000 but the agreed price worked out 10% higher, taxed at 12%.
You enter
You get
Important points to keep in mind
- Debit notes also land in GSTR-1 Table 9B, flagged as debits rather than credits.
- There is no statutory deadline for debit notes, but report them in the period they're issued.
- Rate differences discovered later should use the correct new rate for the additional value.
Frequently asked questions
Debit note vs supplementary invoice — same thing?
Functionally yes; the law uses both phrases for documents that increase a supplied invoice's value.
Can a debit note exceed the original invoice?
It references the original invoice but may exceed it where quantities or prices genuinely increased beyond the initial bill.
Related GST tools
Prepare your returns in GSTSelf
Done estimating? Prepare the actual return.
GSTSelf walks you through your invoices, builds GSTR-1 and GSTR-3B data, and keeps everything on your device — no uploads, no account.