A matter of record
Definition 1 of 1
Pro Tip 1/3Official Confirmation
Use it when you want to state that information has been formally verified or acknowledged. 
His resignation is a matter of record; the company confirmed it last week.
Pro Tip 2/3Not Confidential
Implies that the information is not secret and can be accessed or verified by the public. 
Her speech is a matter of record, available in the library archives.
Pro Tip 3/3Legal Evidence
Often used in legal or official contexts to refer to information that can be used as evidence. 
The contract was signed by both parties and is now a matter of record in the court documents.