Supported document type
Detect tampered and deepfake Quotation
A quotation is a seller's priced offer for named goods or services, valid for a stated period and issued before any order exists. It supports purchases, budgets and financing requests, so forgeries target the arithmetic and the validity terms. Quantity, unit price, discounts and tax have to foot to the total, and the dates have to run in order. A quote that foots still leaves evidence in its layout and in the file itself.
API slug: quotation
Last updated:
What a genuine quotation contains
A genuine quotation carries a seller header with name, address, tax ID and contact details, a quote number and date, and a customer or prepared-for block. Line items give a description, quantity, unit price and line total, followed by a subtotal, tax or VAT, any discounts and a grand total with its currency.
The commercial terms follow: a validity period, delivery and payment terms, and sometimes an acceptance or signature block. Most quotes come out of a CRM, ERP or accounting system with little PDF metadata, so plain layouts are normal. Prices may exclude tax, optional lines and alternates are common, and the quote number usually follows a different series from the seller's invoices.
How quotation forgeries are made
Line and total arithmetic edits
A quantity, unit price or total is changed to inflate a budget or support a financing request. Quantity multiplied by unit price must equal each line total, the line totals must equal the subtotal, and the subtotal less discount plus tax must equal the grand total. One stale figure breaks the chain.
Single-figure patching
A price, quantity or total sits in a different font or alignment from the figures around it, or on a patched background. System-generated quotes are uniform, so a local difference stands out.
Validity and date edits
A quote dated after its own valid-until date, or with an impossible date sequence, shows that a date was changed to make an old or lapsed offer look current.
Seller block replacement
The seller's name, tax ID or contact details differ between the header and the body, or a seller block has been pasted over another. A currency symbol, tax rate or tax label that does not fit the seller's stated jurisdiction points the same way.
Acceptance signature or stamp transplant
An acceptance signature or stamp is placed on a quote that never carried one. It is inconsistent with the rest of the page in resolution and background, even when the numbers above it are untouched.
What TamperCheck checks on a quotation
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.
Letterhead, logo, and issuer plausibility
Issuer branding is checked for resolution and compression consistency against the body text it sits on. A logo lifted from a website carries the signature of its source, not of the document.
And many more checks
The three above are the layers that carry the most weight on a quotation. 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 quotation, and why
Procurement and finance teams, lenders, and buyers comparing supplier quotes. 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 quotation in 4 steps
Recompute every line
Multiply quantity by unit price for each line, add the lines for the subtotal, then apply discount and tax and compare with the grand total, allowing for rounding.
Read the dates in order
Check that the quote date precedes the valid-until date. An already lapsed validity on an archived quote is normal, but an impossible sequence is not.
Compare seller details
Check that the seller's name, tax ID and contact details agree between the header and the body, and that the currency and tax label fit the seller's jurisdiction.
Run a forensic check on the file
The arithmetic gives the logical story and the file gives the edit history. TamperCheck runs 200+ forensic checks including arithmetic validation and patch detection, returning a risk score from 0 to 100 with findings tied to regions of the image.
Frequently asked questions
How do I check that a quotation is genuine?
Recompute it. Quantity times unit price should equal each line total, the lines should add to the subtotal, and the subtotal less discount plus tax should equal the total. Then check that the dates run in order and that the seller details agree between header and body.
Is an expired quotation suspicious?
Not by itself. An archived quote often shows a validity date that has already passed, and a quote is an offer that can be withdrawn. The suspicious signs are a quote date after its valid-until date or an impossible date sequence.
Why does the quote number differ from the seller's invoice numbers?
Sellers usually number quotes in their own series, separate from invoices, so a different format is normal. It is not evidence that the quote is fabricated.
Is a quotation the same as an invoice or a purchase order?
No. A quotation is the seller's priced offer before any order, an invoice is a bill for goods or services delivered, and a purchase order is the buyer's commitment to buy. A contractor proposal with a scope of work narrative is a related but different document.
TamperCheck analyses quotation uploads with a hybrid forensic and AI pipeline tuned for this document class. Upload endpoints accept PDF and common image formats; class is inferred automatically. See the API documentation for authentication, async jobs, and webhooks.