Supported document type
Detect tampered and deepfake Proposal
A contractor proposal is a written offer to do defined work for a stated price, usually for a named project, and owners, lenders and procurement teams rely on it to support a budget or a draw schedule. Forgeries change the price, the scope or the acceptance, because those are the fields a decision rests on. Checking one means testing the arithmetic, the dates and the signature block against each other.
API slug: proposal
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What a genuine proposal contains
A genuine proposal opens with the proposer's name, address, phone and email on a letterhead, followed by a proposal date and the project name and address. The scope of work lists items or trades, often with a price on each line or a single lump sum, and notes which plans or drawings the price relied on.
The conditions carry the weight. Exclusions, assumptions, a validity period and change-order wording for work that differs from the plans sit above a total or contract sum, payment terms and a client acceptance block with a signature and date. The layout is often hand-typed, with uneven spacing, mixed fonts and prices written as lead-ins such as a dollar amount followed by a quantity, and the countersigned copy is frequently scanned after the proposal was issued.
How proposal forgeries are made
Total and line-item edits
Prices are raised or the contract sum is rewritten so the proposal supports a larger budget or draw. The lines then fail to add up to the stated total, or a per-run price multiplied by the run count no longer matches its line amount. Arithmetic on a typed proposal is unforgiving, and one stale figure exposes the edit.
Single-figure patching
One price, quantity or total is replaced in a different font, weight or alignment from its neighbours, or sits on a patched background. Loose, hand-typed layouts make this tempting, but the edited figure still carries its own rendering and sharpening.
Acceptance block transplant
A signature is lifted from another document and placed in the client acceptance block. Its ink, resolution and compression differ from the typed body, which is different from the ordinary case of a signature page that was scanned separately and then attached.
Date manipulation
A signing date earlier than the proposal date, or an acceptance that falls outside the stated validity period, shows a date was changed to make an old offer look live. The proposal date normally precedes the signing date, so the order of the dates is a check in itself.
Letterhead and cover-up edits
The proposer's name, licence or contact details disagree between the letterhead and the body, or an overlaid image hides original text where no stamp, logo or signature belongs. Both leave a boundary that does not match the page beneath it.
What TamperCheck checks on a proposal
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.
Signature forgery analysis
Signature regions are assessed for ink consistency and for how the stroke sits on the page, which distinguishes a genuine pen stroke from a pasted image of one.
And many more checks
The three above are the layers that carry the most weight on a proposal. 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 proposal, and why
Construction lenders, owners, general contractors, and procurement teams reviewing bids. 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 proposal in 4 steps
Add the lines to the total
Sum the scope items and compare the result with the stated total or contract sum. Where prices are given per run, multiply by the run count and compare with the line amount.
Put the dates in order
Check that the proposal date comes first, that any acceptance falls inside the validity period, and that the signing date does not precede the proposal.
Compare the acceptance block with the body
Look at whether the signature and date block share the resolution and compression of the typed text, and whether the proposer's name and contact details agree between letterhead and body.
Run a forensic check on the file
The arithmetic and dates tell the logical story, and the file tells 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 can I tell if a contractor proposal is fake?
Start with the numbers. A genuine proposal's line items add up to its total, its dates run in order, and its letterhead and body agree on who the proposer is. A figure in a different font, a signature block with different image quality from the body, or an overlay hiding original text are the usual signs of an edit.
Why is the signing date later than the proposal date?
That is the normal order. A proposal is issued first and countersigned by the client afterwards, so a signing date that follows the proposal date is expected. The suspicious case is the opposite, a signing date earlier than the proposal or an acceptance outside the validity period.
Can a scanned proposal with a signed page still be genuine?
Yes. Proposals are often printed, signed and scanned, so the signature page can have a different resolution from the typed body without anything being wrong. What matters is whether a specific figure or block shows its own edit traces, not whether pages differ in scan quality.
Does an authentic proposal prove the work was done?
No. A proposal is an offer. An authentic one says nothing about whether the work was carried out or paid for, so a lender or owner still needs the contract, invoices and payment records to support a draw.
TamperCheck analyses proposal 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.