A New York Certificate of Proof of Execution By A Subscribing Witness is a legal document that serves as a record of a contract, agreement, document, or other written instrument having been executed by one or more parties. This document is completed and signed by a subscribing witness who has personally observed the signing of the instrument. There are two types of New York Certificate of Proof of Execution By A Subscribing Witness: Single Witness and Multiple Witness. The Single Witness Certificate is used when one subscribing witness is present to observe the signing, while the Multiple Witness Certificate is used when two subscribing witnesses are present. Both certificates must be signed by the subscribing witnesses, and include the names of the parties signing the document, the date of the execution, and the title of the document. The New York Certificate of Proof of Execution By A Subscribing Witness is used to prove to third parties that the document was signed in accordance with the law.