Let’s Seal

Seal and verify procurement & tender documents

Purchase orders, tender submissions, invoices, and certificates of origin that prove their own authenticity — so a buyer, a supplier, or a bank can confirm a document is genuine and was submitted on time. Altered invoices and backdated tenders fail on sight.

For buyers, suppliers, tender teams, and trade-finance desks.

Open the app Developer docs
What a seal proves

Four guarantees, in procurement & supply chain

Documents that can't be altered

A changed price, quantity, or bank detail fails verification. Invoice-redirection fraud and doctored POs are caught at the source.

The issuing party, named

Every PO, invoice, and certificate names the organisation that sealed it, chaining to a published root — provable issuer, not a spoofed template.

Submitted on time, provably

A tender or bid is timestamped on Bitcoin the moment it's sealed — independent proof it existed before the deadline, settling any dispute over lateness.

Verified by the counterparty, free

A buyer, a supplier, or a trade-finance bank confirms a document at a permalink — instantly, and free.

How it works

From your file to a proof anyone can check

The same pipeline every time — the seal and the timestamp travel with the file, so the proof is self-contained.

Your file
Your signed PDF
Seal
Signed over every byte · PAdES
Anchor
Bitcoin timestamp + public transparency log
Proof page
A permanent /d/… link travels with the file
Anyone verifies
Free, public, offline-capable — for anyone
The proof travels inside the file. Verification stands on the published root, the transparency log, and the Bitcoin ledger — so a court, a bank, or a counterparty can check it independently, forever.
Step by step · the web app

Seal it in the app — no setup

  1. 1

    Sign in as your organisation

    Open app.letsseal.org and sign in. Your organisation gets its own certificate authority for sealing procurement documents.

  2. 2

    Seal the document

    Upload the tender, PO, or invoice. It's sealed with your certificate over the whole file, so any later edit is caught — and, for a tender, timestamped as proof of submission time.

  3. 3

    Anchored and logged automatically

    The fingerprint is timestamped on Bitcoin and written to the public transparency log. The counterparty gets a normal PDF that also verifies.

  4. 4

    Send with a proof link

    Every document has a permanent proof page. The buyer, supplier, or bank opens the link to confirm it's genuine and, for a tender, on time.

Step by step · the CLI

Automate it from your terminal or CI

The sealbot CLI does the same thing, scriptably — one command per file, straight into your pipeline.

# Timestamp a tender submission — proof it existed before the deadline
$ sealbot seal tender-submission.pdf --org examples
sealed   tender-submission.pdf
  proof  https://letsseal.org/d/1b73ce…d902
  anchored to Bitcoin · recorded in the transparency log

# Seal every outbound invoice automatically
$ sealbot watch /srv/invoices --mode seal --org examples
watching /srv/invoices … sealing new & changed PDFs (idempotent)

# A buyer confirms an invoice — public, no account
$ sealbot verify invoice-88231.pdf
✓ authentic · unaltered · sealed by Let's Seal Examples

Seal a tender to prove when it was submitted; seal invoices and POs so a counterparty can verify they're genuine and unaltered — one command per document, no per-seal fee.

Full CLI & API reference
See it in action

What a proof looks like, and what you can seal

Issuer verified — controls letsseal.org
Authentic & unaltered
Document
A timestamped tender submission
Issuer
Let’s Seal Examplesletsseal.org
SHA-256
64-hex fingerprint ✓

Anchored on Bitcoin

Recorded in the public transparency log

Public and free to verify — by anyone, with standard tools.
Open the live proof

A single use case, many documents. Each of these is sealed the same way:

  • A timestamped tender submission

    Live proof

    Open the proof page the way a procurement panel would: it shows the bid is authentic, unaltered, and — decisively — timestamped on Bitcoin before the deadline, settling any dispute over lateness.

  • An invoice

    Seal outbound invoices so a buyer can confirm the amount and bank details are exactly as issued — the direct defence against invoice-redirection fraud.

  • A purchase order or contract

    Seal POs and NDAs so both sides can prove the terms are exactly as agreed, and which version was issued.

  • A certificate of origin or delivery note

    Trade documents sealed and dated, so a customs officer or trade-finance bank can verify they're genuine and unaltered along the chain.

Live proofs are real documents sealed under the “Let’s Seal Examples” organisation.

Common documents

What you’ll seal

  • Purchase orders
  • Contracts & NDAs
  • Tender submissions
  • Invoices
  • Certificates of origin
  • Delivery & goods-received notes
Questions

Straight answers

Can this prove a tender was submitted on time?
Yes. Sealing a tender timestamps it on Bitcoin the moment it's sealed — independent evidence it existed before the deadline, which settles a dispute over whether a bid was late.
How does this help against invoice fraud?
A sealed invoice can't be edited — a changed amount or bank detail fails verification — and the buyer can check it against the proof link. Invoice-redirection fraud, which relies on altering a genuine invoice, is caught.
How does a counterparty verify a document?
They open the proof link, or drop the PDF into the public verifier. It confirms the document is genuine, unaltered, and issued by you — with no call required.
Can I seal every invoice automatically?
Yes. Point the CLI or a watched folder at your finance system and every invoice leaves sealed, timestamped, and carrying a proof link — one command per file, no per-seal fee.

Start sealing procurement & supply chain documents

Free and open. Seal in the app, automate from the CLI, and hand anyone a proof they can verify themselves.

Open the app All use cases