1) Why the signature matters

A promissory note is commonly used in Philippine lending as the borrower’s written promise to pay a sum of money. In the legal sense, however, a “promissory note” can function in two overlapping ways:

As a negotiable instrument under the Negotiable Instruments Law (NIL), Act No. 2031, which gives it special commercial characteristics (transferability, presumptions, “holder in due course” rules, etc.); and/or
As evidence of a loan or debt under the Civil Code, where the core issue is whether an enforceable obligation exists, regardless of negotiability.

The borrower’s signature is pivotal in both—but in different ways.

2) The governing rules in the Philippines

A. Negotiable Instruments Law (Act No. 2031)

Two NIL principles drive the analysis:

A promissory note must be “signed by the maker” to be negotiable. Under Section 1, an instrument is negotiable only if it is in writing and signed by the maker or drawer, among other requirements.
No one is liable on an instrument unless their signature appears on it. Section 18 states the foundational rule: a person is not liable on the instrument whose signature does not appear thereon, subject only to specific NIL exceptions.

Practical consequence: If the principal borrower (the intended maker) did not sign, then—as a negotiable instrument—the note generally cannot be enforced against that borrower as the maker.

B. Civil Code (Republic Act No. 386)

Even when a document fails as a negotiable instrument, an obligation may still exist under civil law:

Contracts generally require consent, object, and cause (Civil Code Art. 1318).
A simple loan (mutuum) is traditionally treated as a real contract—it is perfected upon delivery of the money. Once money is delivered and received, the obligation to repay can exist even if the promissory note is defective or unsigned, provided the loan can be proven by other evidence.

Practical consequence: An unsigned promissory note may be weak or useless as a “note”, but it does not automatically erase a loan if the lender can prove delivery/receipt and the terms (or at least the principal amount).

3) The core question: Is an unsigned promissory note “valid”?

It depends what “valid” means.

A. Valid as a negotiable promissory note (NIL)?

Usually, no—if the principal borrower’s signature is absent.

Without the maker’s signature, the document generally fails the NIL requirement of a negotiable instrument (Sec. 1).
The absent-signature borrower is generally not liable “on the instrument” (Sec. 18).

B. Valid as a binding written promise by the borrower?

Usually, no—at least not as that borrower’s written undertaking, because the signature is the usual marker of assent and authorship. If the borrower never signed (and no authorized agent signed for them), it is difficult to treat the document as the borrower’s own written promise.

C. Still usable as evidence of a loan or obligation?

Sometimes, yes—but the lender must usually prove the obligation through other facts and documents (delivery of funds, acknowledgments, partial payments, admissions, account statements, messages, receipts, etc.). The unsigned note may still have some evidentiary value (e.g., it memorializes terms the lender alleges), but standing alone it is typically not enough to prove the borrower’s assent.

4) Common scenarios and how Philippine law typically treats them

Scenario 1: The principal borrower never signed, and nobody signed on their behalf

NIL: Borrower is not liable on the instrument (Sec. 18).
Civil law: Borrower may still be liable if a loan is proven (delivery/receipt). The case becomes a standard collection case based on loan, not enforcement of a negotiable instrument.

Scenario 2: The borrower did not sign, but a “co-maker” or “surety” signed

This is extremely common in Philippine promissory notes.

The signatory (co-maker/surety) can be liable because their signature appears on the document (NIL Sec. 18).
Whether the signatory’s liability is principal (solidary) or accessory (surety/guaranty) depends on the wording:
- If the signatory signed as co-maker and the note states “We jointly and severally promise to pay…” or similar, that signatory is typically treated as a solidary debtor—liable for the whole amount.
- If the signatory signed as surety, they may still be directly liable, often solidarily by the suretyship terms, but conceptually the obligation is accessory to a principal obligation.

Important nuance: A suretyship/guaranty is accessory; it presupposes a principal obligation. Even if the principal borrower didn’t sign the note, a principal obligation might still exist (e.g., a proven loan by delivery of funds). If no principal obligation exists at all, accessory liability is vulnerable.

Scenario 3: The borrower’s name is typed/printed but not signed

A typed name, by itself, is not automatically a signature in the NIL sense. The issue is intent to authenticate.

For traditional paper notes, courts commonly look for an actual signature or mark placed with intent to sign.
A purely typed name on paper, without more, is usually not treated as a signature.

Scenario 4: The borrower “initialed” pages but did not sign the signature line

Initials can sometimes function as a signature if intended to authenticate the instrument as a whole. But it is fact-specific:

Initials placed merely to indicate page review may be argued as insufficient.
Initials placed in a manner showing final assent may support enforceability (particularly under civil law evidentiary analysis), but enforcing it as a negotiable instrument is harder unless the initials clearly serve as the maker’s signature.

Scenario 5: The borrower’s signature is a thumbmark or “X” mark

A signature is not limited to cursive writing. A mark can qualify if:

It was made or adopted by the person, and
Intended to authenticate the instrument.

Scenario 6: The borrower did not sign—but an authorized agent signed

Under the NIL, a signature may be made by an agent (Section 19). The key is authority and how the signing is reflected:

If an authorized agent signs the principal’s name (or clearly signs in a representative capacity), the signature can bind the principal.
If the agent signs only their own name, the principal’s liability may be disputed unless the instrument clearly shows the agent signed on behalf of the principal; otherwise the agent can be personally liable (NIL Section 20 issues often arise here).

Corporate borrowers: If the “borrower” is a corporation, it signs through authorized officers. Authority commonly comes from board resolutions, secretary’s certificates, or bylaws/delegations. Lack of authority can shift liability to the signing officer depending on circumstances and how they signed.

Scenario 7: The borrower’s signature is forged

Forgery is governed by NIL Section 23: a forged signature is generally inoperative and does not bind the person whose signature was forged, subject to exceptions based on estoppel or preclusion in particular circumstances.

Result: the principal borrower is generally not liable on the note if their signature is forged, even if the lender acted in good faith—though other signatories may still be liable if their signatures are genuine.

Scenario 8: The borrower didn’t sign, but made partial payments

Partial payment is powerful evidence under civil law:

It can show acknowledgment of debt and assent to repayment.
It may help prove the existence of the loan and sometimes the applicability of terms (interest, maturity), depending on accompanying receipts, communications, and consistent conduct.

It does not magically supply a missing NIL signature, but it can significantly strengthen a civil collection case.

5) What the lender can sue on when the borrower didn’t sign

When the note is unsigned by the intended borrower, lenders typically pivot to one (or more) of these bases:

Action on the loan (mutuum) — prove delivery/receipt and unpaid balance.
Action on written contracts other than the promissory note — loan agreements, disclosure statements, credit line agreements, board resolutions, deeds, security documents.
Quasi-contract / unjust enrichment principles — in some fact patterns, especially where receipt of funds is clear but documentation is defective.

Bottom line: The missing signature usually destroys the easiest path—collection “on the note as negotiable instrument”—but it does not necessarily destroy the debt itself.

6) Evidence and burden of proof in Philippine litigation

A. What the promissory note normally provides (when properly signed)

A properly executed negotiable instrument supplies:

Clear proof of the obligation and terms;
NIL presumptions (e.g., consideration) in favor of enforcement against signatories; and
A straightforward documentary foundation for collection.

B. What changes when the borrower didn’t sign

Without the borrower’s signature:

The lender cannot rely on NIL liability against that borrower (Sec. 18).
The lender must establish, through competent evidence, that:
- money was delivered to and received by the borrower (or for the borrower’s benefit), and
- repayment is due, and
- the borrower failed to pay.

Typical evidence includes bank transfer records, acknowledgment receipts, email/messages, account ledgers, disbursement vouchers, delivery instructions, witness testimony, demand letters and responses, and payment history.

7) Special note on electronic promissory notes and e-signatures (Philippines)

The Philippines recognizes electronic data messages and electronic signatures under the E-Commerce Act (RA 8792) and its implementing rules. In electronically executed lending:

An “electronic signature” can satisfy signature requirements if it is shown to be the act of the person with intent to authenticate (often supported by audit trails, OTP logs, platform records, or certificate-based signatures).

So a promissory note that appears “unsigned” in the traditional ink sense may still be “signed” electronically—depending on the system used and proof available.

8) Remedies and defenses commonly raised

A. Lender remedies (typical)

Collection of sum of money (ordinary civil action), sometimes with:
- claims for stipulated interest (if proven),
- legal interest (if no valid stipulation is proven), and
- attorney’s fees (only when contractually stipulated and reasonable, or allowed by law and properly justified).

B. Borrower defenses (typical in missing-signature cases)

No consent / not my obligation (especially if no receipt of funds is proven).
No authority (if someone else signed).
Forgery (if signature appears but is not genuine).
Payment / partial payment disputes.
Unconscionable interest or invalid penalty clauses (fact- and jurisprudence-dependent).
Failure to prove delivery/receipt (critical where the note is unsigned).

9) Interest, penalties, and attorney’s fees when the note is unsigned

A. Stipulated interest

Philippine law allows stipulated interest, but it must be:

Proven, and
Not contrary to law, morals, good customs, public order, or public policy.

If the borrower didn’t sign the note, proving the borrower agreed to the stated rate becomes harder unless there is another signed agreement or strong evidence of assent.

B. Legal interest (default interest)

When there is no enforceable stipulation as to interest, courts may apply legal interest depending on the nature of the obligation and jurisprudential rules on forbearance of money. (Bangko Sentral ng Pilipinas issuances have historically set default legal interest levels; these can be updated over time.)

C. Attorney’s fees

Even if written in a document, attorney’s fees are not automatic; they must be reasonable and justified, and courts can reduce or deny them.

10) Practical drafting and compliance points (what typically prevents “unsigned borrower” disputes)

Clear signature blocks with printed name, valid ID details, and witnessed signing where feasible.
Representative capacity indicated for agents and corporate signatories, with supporting authority documents (e.g., SPA, board resolution, secretary’s certificate).
Consistent documentation: promissory note + loan agreement + disclosures + disbursement records.
Electronic execution safeguards: reliable authentication, audit trails, tamper-evident records.
Avoid blank or incomplete instruments; NIL rules on incomplete instruments and delivery can complicate enforcement.

11) Key takeaways (Philippine context)

Against the principal borrower, an unsigned promissory note is generally not enforceable “on the instrument” because the NIL requires the maker’s signature and imposes liability only on those whose signatures appear (NIL Secs. 1 and 18).
The debt may still be enforceable under civil law if the lender can prove the loan (especially delivery and receipt of funds) through other competent evidence.
Any person who did sign (co-maker, surety, guarantor, accommodation party, agent, corporate officer) can be liable according to the capacity and wording of the instrument and applicable civil law rules.
Authority, authenticity, and proof are the decisive battlegrounds in missing-signature cases: who signed, with what authority, and what evidence proves the borrower received the money and agreed to repay under specific terms.