"Formal notice" refers to a written or verbal message that is official and often has legal significance. It is a formal way of informing someone about a specific matter or action that is required or expected from them. Full definition
The party did not issue formal notice of its dissolution, but the organization's website was inactive as of 2013. (ballotpedia.org)
Next, you'll give formal notice to the insurance company by writing a letter. (chicagolawyer.com)
You want create a document for use by directors or shareholders to waive their right to receive formal notice of a corporate meeting. (rocketlawyer.com)