Wet signature vs electronic signature: what actually changes

A wet signature is a physical act; an electronic signature is data. Regulation (EU) No 910/2014, article 25(1), settles the phobia: no electronic signature may be denied legal effect and admissibility as evidence solely for being electronic. The wet side never needed such a rule — the question was never wet-or-invalid. The real difference is evidentiary: what happens when someone later challenges who signed, or whether content changed, or when.

On proof, the electronic side can carry facts the wet side cannot self-produce: a cryptographic binding of content to the step at signing, a verifiable time from an authority, and a chain logging the ceremony. What it cannot do by itself is satisfy whoever asks for a qualified tier or an ink act — that the law grades explicitly.

Ink on a page — the signature everyone assumed for centuries: physical, occasionally witnessed, kept as paper or as a scan. The act shows willingness; it does not itself bind the ink to the words around it in any checkable way. A scan is just an image: it can be cut, pasted onto another document and printed again without visible traces — reconstruction from the image alone can never know.

What a wet signature leaves unclear, a wet vendor cannot fix after the fact: precedence (which page was printed when), time (whenever the scanner claims), and the gap between the agreed version and the version that went into the drawer. These are not attacks; they are ambiguity costs that dispute resolution absorbs years later.

The three things a wet file cannot self-prove — identity-binding (whose key), content-binding (digest over the signed byte range), and time (authority-stamped UTC) — plus the ceremony trail around them. One check under any validator — Adobe Reader, the European Commission's DSS validator — either re-verifies the whole thing or says precisely which of the three fails.

On retention: an electronic envelope also solves the paper problem the wet route silently accumulates — original, per-signature revisions, sealed final carried in one evidence pack, kept under the customer's retention settings and purged with cryptographic proof of erasure. A scan of a wet contract stores an image; the evidence around it lives elsewhere or not at all.

Notarial deeds, civil-register acts, and other procedures keep handwritten signatures in member-state law; those are simply outside the ordinary e-signature envelope. Inside the digital envelope, the graded tier exists precisely for such questions: an advanced-with-qualified-certificate or a qualified electronic signature may be demanded in defined cases — for online public-sector services, article 27(1)–(2) states which tiers a member state may require and which it must recognise.

The Portugal-specific layer: Decreto-Lei n.º 12/2021 article 3(2) attaches a legal presumption to the qualified electronic signature, and article 3(5) gives electronic documents the probative force of signed private documents via article 376 of the Civil Code. In the US, 15 U.S.C. §7001(a) denies validity to the argument 'it was only electronic'.

For ordinary commercial, HR and B2B documents, an advanced signature with a complete evidence pack is the norm; for notarial and constitutionally significant acts, ink stays. Anything else where a counterparty demands the qualified tier is a red line to check before sending — not after signing.

Remote counterparty, no shared office, time-sensitive deal: electronic. The counterparty signs from their phone with no account; the evidence pack arrives complete; verification runs publicly. Wet ink cannot travel to them through a scanner without losing its three facts.

Notarised or register-bound acts: wet ink (or a qualified tier where the act's regime supports it). Commercial contracts with a demanding counterparty: electronic with strong evidence — offer the verification path; disputes about whether the signature 'is real' have already been answered by the digest.

The deliberate in-between: some companies keep wet on their template and archive the signed paper as a scan because a legacy clause requires it ('the contract is done on paper'). If ten years of civil procedure is the horizon, prefer the tiered route — a wet scan tells a verifier nothing the image does not show.