Short answer. Deny it under oath, specifically, and state your version of the facts. Under Rule 8, Section 8, the genuineness and due execution of a written instrument sued upon are deemed admitted unless you specifically deny them under oath and set forth what you claim to be the facts. An unverified general denial admits the document.
What the law says
the genuineness and due execution of the instrument shall be deemed admitted unless the adverse party, under oath specifically denies them, and sets forth what he or she claims to be the facts
Rule 8, Section 8 — How to contest such documents. Read the full provision →
What the law says
the requirement of an oath does not apply when the adverse party does not appear to be a party to the instrument or when compliance with an order for an inspection of the original instrument is refused
Rule 8, Section 8 — How to contest such documents. Read the full provision →
The default is admission
Rule 8, Section 8 works by default, and the default favours the document. Where a claim or defence is founded upon a written instrument attached to the pleading, the genuineness and due execution of the instrument shall be deemed admitted unless properly contested. Deemed admitted means the fight over whether you really signed the thing can be over before it starts — not because a judge weighed the evidence, but because the answer was drafted wrong. Ignoring the attachment, or denying it only in passing, is how defendants lose the forgery issue without a hearing.
The three requirements of an effective denial
An effective contest has three parts, all in the section's words: the adverse party under oath specifically denies them, and sets forth what he or she claims to be the facts. Under oath means the denial must be sworn, not merely pleaded. Specifically means aimed at the document: a general denial of everything in the complaint does not reach genuineness and due execution. And setting forth the facts means telling your version — that the signature is not yours, that the document was altered, whatever you actually claim happened. Miss any one of the three and the deemed admission stands.
What the admission covers
Note precisely what the deemed admission covers: the genuineness and due execution of the instrument — that the document is authentic and was executed as it appears. The section speaks of those two matters and no others, which is why the careful move is to treat the document question as its own battle inside the answer, with its own sworn, specific denial, separate from everything else you dispute in the case. A pleader who conflates attacking the document with attacking the claim tends to do neither properly.
The two exceptions to the oath
The oath is excused in two situations the section itself names: when the adverse party does not appear to be a party to the instrument, and when compliance with an order for an inspection of the original instrument is refused. The first protects strangers to the document — someone sued on a contract they never appear on cannot be made to swear about its execution. The second polices fairness: a claimant who will not produce the original for inspection when ordered loses the benefit of the deemed admission. Outside those two, the oath requirement is strict, and it is the commonest place answers go wrong.