DEFINITION of 'Countersignature'
An additional signature on a document that has already been signed. The countersignature is provided as confirmation or authentication. In most cases, countersignatures are provided by an official or professional, such as a doctor or attorney. This is done to certify that the action or provisions in the document have been approved by both the signer and the other pertinent party.
BREAKING DOWN 'Countersignature'
Countersignatures are required on many different types of documents. Some countries require countersignatures on passports, and many types of domestic health and legal documents require countersignatures as well. Mortgage paperwork often requires countersignatures in various situations.