Wiktionary
n. a temporary policy, used to provide insurance cover while the main policy formalities are finalised.
Usage examples of "cover note".
She should write some sort of cover note to go with the returned garden plans.
A handwritten cover note - every page in the envelope was a photocopy, not an original - showed that the professor of pathology had gotten the copies from his friend, the state medical examiner, and could Sam please be careful how he handled this.
He enclosed a cover note, explaining in his clerkly style that it was of course only a rough estimate, and that I wasn't beholden to reimburse him penny for penny.
She reached for an envelope, dropped the item into it along with a cover note of her own, and sent it on its way back to Grantville and Tony.
Something Ryan had not seen was the cover note from the station chief in Moscow saying that to get his latest signal out, CARDINAL had bypassed half the courier chain that ran from the Kremlin to the U.
If there was another message with this one, containing the message itself and the name of the person to whom it should be delivered, why would this cover note be needed?