Signature forgery is a crime committed when a person signs another party's name or alters a document in order to commit fraud or deceive others. One common example of signature forgery involves check writing. If a person signs the name of the checking account holder to a check without the account holder’s permission, this is considered signature forgery. Likewise, signing another person’s signature to a range of other written documents without his permission also constitutes signature forgery.
The purpose or intent of signing another person’s name to a document is key in determining whether or not it is considered signature forgery. In most jurisdictions, the signer has to intend some type of deceit or plan to commit fraud for it to be considered forgery. Incidents in which a person has permission to sign another party’s name are not considered a crime.
An act can be considered signature forgery without regard to whether or not the entire signed document was created fraudulently — a forgery may occur if a person creates an entire document and signs someone else’s name to it. Many jurisdictions also consider it forgery, however, if a person alters a legitimately signed document by erasing, inserting, or changing any part of it without the signer’s knowledge and consent. Additionally, the document in question need not be a legal contract or other legal document for it to be considered forgery. A falsely signed or altered letter may be considered forgery as well.
Sometimes signature forgery occurs when a person abuses the trust another party has placed in him. For example, if one person asks another to draft a will for him, and the creator adds information that differs from what the requester specified, this may be considered fraudulent activity in some places. In fact, it may be considered forgery even if the person who requested the will signs it.
In some jurisdictions, the crime of forgery may be committed even if a document containing a forged signature is not used or published. For example, signing a check with the intent to commit fraud may lead to forgery charges even if a bank refuses to cash the check. Likewise, altering a legitimately signed document for the purpose of committing fraud may be enough to warrant forgery charges in some places, even if the crime is discovered before the signer suffers any harm. An individual may even be charged with a crime for possessing forgery tools with the intent to use them or allow another person to use them.