Digital Signatures on Quotes — How It Works

Every tradesperson has been through this: "He said yes over the phone." And then the client doesn't remember the price, the scope, or the terms. PresuNow includes digital signatures with SHA-256 hash, IP logging, timestamp, and full audit trail on every quote. In Spain, over 60% of disputes between professionals and clients are due to undocumented verbal agreements. With PresuNow, the client signs on screen, the document is digitally sealed, and there's no room for misunderstandings.

The problem with verbal agreements

The most common scenario: you visit the client, explain the job, give them a price verbally. "Yes, go ahead, whenever you can." You start. Halfway through the job, the client says the price was different. Or that a certain item wasn't included. Or that you promised something you never said.

You have nothing signed. It's your word against theirs.

The WhatsApp variant is just as fragile. An "ok, go ahead" in a chat doesn't specify what was accepted. It doesn't detail the price, the line items, or the payment terms. If there's a dispute, a WhatsApp message doesn't prove the client accepted a specific quote with specific conditions.

The real problems caused by verbal agreements:

• The client denies agreeing to the final price
• Arguments over what was included and what wasn't
• Partial non-payment with no proof of what was agreed
• Time wasted on claims that go nowhere
• Professional and personal burnout

The solution isn't complicated: have the client sign the quote before you start. But it has to be easy. If you send them a PDF and ask them to print it, sign it, scan it, and send it back, they won't do it.

How digital signatures work in PresuNow

The process is designed so the client signs in under 30 seconds, from their own phone.

1. You send the quote. Via WhatsApp, email, Signal, Telegram — any platform. PresuNow generates a shareable link with one click.

2. The client opens the link on their phone. No app to install. No account to create. No login needed. They open the link and see the quote directly in their browser.

3. The client reviews the quote. They see all the line items, prices, payment terms, scope, and exclusions. Everything you've chosen to show in the client view.

4. The full-screen signature panel appears. A touch-friendly area where the client signs with their finger. Large, comfortable, designed for mobile.

5. At the moment of signing, the SHA-256 hash is generated. This is what makes the signature technically robust. The system calculates a cryptographic hash of the exact document the client is accepting. If anyone modifies a single comma after the signature, the hash won't match. The document is sealed.

6. The system records all identification data. Client's IP address, exact timestamp, browser details, device information. Everything is linked to that specific signature.

7. The signature is stored securely. In a private storage bucket, separate from the rest of the data. Restricted access.

8. Both parties receive confirmation. You receive a push notification and email that the quote has been accepted. The status changes automatically on your dashboard.

9. Everything is recorded in the quote's timeline. Every event — creation, sending, viewing, signature — appears in a chronological history with timestamps and details.

Is it legally valid?

Yes. In Spain, electronic signatures are regulated by the eIDAS Regulation (EU Regulation 910/2014) and Law 6/2020 of 11 November, which transposes the European framework into Spanish law.

The regulations distinguish three levels of electronic signature:

1. Simple electronic signature — Any electronic data attached to or associated with other data that the signatory uses to sign. The most basic.
2. Advanced electronic signature — Uniquely linked to the signatory, capable of identifying them, and detects any subsequent changes to the signed data.
3. Qualified electronic signature — Requires a qualified certificate and a qualified signature creation device (e.g. Spain's electronic national ID, DNIe).

PresuNow's signature constitutes a simple electronic signature with advanced elements. It includes:

• Intent to sign: the client performs a deliberate action (tracing their signature on screen)
• Identification data: IP, device, browser, timestamp
• Document integrity: SHA-256 hash that detects any subsequent modification

It is not a qualified signature (it doesn't use the DNIe digital certificate), but it is legally admissible for commercial agreements between professionals and clients. Article 25.1 of the eIDAS Regulation expressly states that an electronic signature shall not be denied legal effect solely on the grounds that it is in electronic form or that it is not a qualified signature.

In practice, for trade quotes between a professional and a private individual, a simple electronic signature with full audit trail is sufficient and valid.

What is recorded when the client signs

It's not just an image of the signature. The system captures and stores:

SHA-256 hash of the document. A cryptographic hash of the exact quote at the moment of signing. It's a digital fingerprint of the document. If anyone modifies any data afterwards — a price, a description, a condition — the hash changes. The signature is only valid for the original document.

Client's IP address. The IP from which the client accesses and signs. Serves as additional identification data and approximate geolocation.

Exact timestamp. Precise date and time of the signature. It's not the server time — it's the exact moment recorded by the system.

Browser and device details. Browser type (Chrome, Safari, Firefox...), operating system, device type (mobile, tablet, desktop). Data that helps verify the identity and circumstances of the signature.

The digital handwritten signature. The image traced by the client on the touch panel. Stored in a private and secure bucket, separate from the rest of the quote data.

Together, this forms a solid evidence package. It's not just "the client signed". It's "the client signed this exact document, from this IP, at this time, with this device, and the document has not been modified since".

The full workflow: from quote to signed agreement

Step by step in a real case:

1. You create the quote in PresuNow (manually, by voice, or from a template)
2. You review the client view to confirm they see the right information
3. You tap "Share" — a message with link and your logo is generated
4. You send via WhatsApp (or email, Signal, whichever platform you use)
5. You receive a notification when the client opens it ("Viewed")
6. The client signs on their phone
7. You receive an acceptance notification
8. The quote moves to "Accepted" status with full audit trail

If the client doesn't sign, you schedule an automatic follow-up. PresuNow notifies you when it's time to send the reminder, with a pre-written message and direct link.

If the client declines the quote, the status changes to "Declined" and it's recorded in the timeline. You know exactly when and what happened.

Why it matters: real scenarios

The client who "doesn't remember" the price. With a digital signature, the price is in the signed quote. No room for interpretation. Open the app, show them the document with their signature and all the data.

The extra work that "was included". If the scope and exclusions are in the signed quote, the discussion is short. What's in there is in there. What's not is a new quote.

The non-payment that ends in a claim. If you need to make a claim, you have a signed document with SHA-256 hash, IP, date, time, and device. Much stronger than an "ok sure" on WhatsApp.

It's not about distrusting the client. It's about professionalising the relationship from the start. A signed quote protects both parties.

Frequently asked questions

More related guides

• Send quotes via WhatsApp — How to share professional quotes with an interactive link
• From quote to invoice — How to invoice from an accepted quote (full, partial, or by line item)
• Best quoting app for freelance tradespeople — Complete comparison of tools in 2026