# Detect tampered and deepfake Credit Note > A credit note reduces what a customer owes on an invoice, and a debit note raises it. Both change money, so both get forged: a fake credit note reverses a genuine invoice, and an altered one cancels more than was agreed. The document is an invoice in miniature, tied to an original invoice number, with line and tax arithmetic that has to close and a sequence number that has to make sense. **Canonical URL:** https://tampercheck.ai/documents-support/credit_note **API document class:** `credit_note` --- ## What a genuine credit note contains A credit note carries the issuer's details and tax registration, the customer's, a note number and date, and a reference to the original invoice it adjusts. It gives the reason, such as returned goods, a pricing correction, or a discount, lists the adjusted lines with quantities and prices, and shows tax and the net credit. A debit note follows the same layout in the opposite direction. The note is bound to its invoice. The referenced invoice must exist, its date must precede the credit note, and the credit should not exceed the original amount unless several notes are being applied. Lines multiply out, tax follows the invoice's rate, and the note number belongs to the issuer's sequence for that period. A number outside the range, or a tax registration that does not match, deserves attention. ## How credit note forgeries are made ### Credit amount inflation A credit is raised beyond the original invoice, or a note is created for an invoice that was paid in full. Totals fail against the referenced invoice and the changed digits are set differently from their lines. ### Reversal of a paid invoice A fabricated note cancels an invoice so payment is withheld or refunded. The issuer's ledger has no matching note number, and the layout departs from their usual output. ### Tax line manipulation The tax reversal is altered to claim a larger refund. Tax no longer equals the rate times the credited lines. ### Sequence and date anomalies Numbers or dates are changed to slot a note into a period it does not belong to. The number falls outside the issuer's range for the month or precedes the invoice it credits. ## What TamperCheck checks on a credit note TamperCheck runs 200+ forensic checks across three layers and returns a risk score from 0 to 100 with plain-English findings tied to specific regions of the document. These three carry the most weight on this document class. ### Arithmetic reconciliation Stated totals are recomputed from their components, and running or cumulative figures are checked for continuity across periods. A single edited value breaks the chain even when the page still looks right. ### Table structure integrity Inserted and deleted rows leave structural artifacts behind: inconsistent spacing, misaligned columns, and formatting the visible table no longer accounts for. ### Date and validity consistency Issue, expiry, and period dates are checked against one another and against the file's own creation metadata, which catches backdating and validity extension. ### And many more checks The three above are the layers that carry the most weight on a credit note. Every upload runs the full suite of 200+ checks regardless of document class, spanning file structure and metadata, pixel-level forensics, font and text rendering, optical and print characteristics, provenance signals, AI-generation signatures, and many more checks. ## Who verifies a credit note, and why Accounts payable teams, auditors, and tax reviewers. In each case the document is being used to unlock money, access, or a legal status, which is exactly what makes it worth forging. ## How to verify a credit note in 4 steps 1. **Check the fields against each other.** Read credit amount, original invoice reference, and tax lines together rather than one at a time. Forgers typically change one value and leave the rest of the document describing the original. 2. **Inspect the file metadata.** Open the document properties and look at the producer, creation date, and modification date. A document produced by a consumer PDF editor, or created long after the date printed on its face, is worth a closer look. 3. **Ask for a second document.** Request a corroborating document from the same issuer or an adjacent period. Forgery effort concentrates on one file, so inconsistencies surface as soon as there are two to compare. 4. **Run a forensic check.** Manual review catches obvious edits but not field-level pixel manipulation or synthetic generation. TamperCheck runs 200+ forensic checks on a credit note and returns a risk score from 0 to 100 in about a minute, at $0.50 per document. ## Frequently asked questions ### How do finance teams detect a fake credit note? They match it to the original invoice and the issuer's ledger, then test the arithmetic and the sequence number. A credit note that exceeds its invoice, or carries a number the issuer never used, is the classic failure. ### What is changed on a forged credit memo? The credit amount, the referenced invoice, the tax lines, and the date. Each affects how much the payer deducts or reclaims, so those fields deserve field-level scrutiny of the PDF. ### What is the difference between a credit note and a debit note? A credit note reduces the amount a customer owes, for example after a return. A debit note increases it, for example to add a charge that was missed. Both refer to an original invoice and both need to reconcile with it. ### Is a credit note the same as a refund? No. A credit note adjusts the amount owed on the books. A refund is the movement of money back to the customer. A credit note may be applied against future invoices without any cash leaving, which is why it needs its own verification. ## Related document types - Invoice: https://tampercheck.ai/documents-support/invoice - Receipt: https://tampercheck.ai/documents-support/receipt - Purchase Order: https://tampercheck.ai/documents-support/purchase_order - Cheque: https://tampercheck.ai/documents-support/cheque - Wire Transfer: https://tampercheck.ai/documents-support/wire_transfer - Payment Schedule: https://tampercheck.ai/documents-support/payment_schedule --- Try TamperCheck now: https://tampercheck.ai/dashboard · Docs: https://tampercheck.ai/docs · Pricing: https://tampercheck.ai/pricing