written proof
nounUK /ˈrɪt.ən pruːf/
US /ˈrɪt̬.ən pruːf/
Written proof is a paper or message that shows something is true.
The teacher asked for written proof that I had permission to leave early.
OTHER MEANINGS
2. A signed paper that shows an agreement or permission is real.
We kept the written proof of the house rental in a safe place.
3. A note from a doctor or parent that explains something.
He brought written proof from his doctor to miss gym class.
4. A message in writing that proves who said or did something.
The email was written proof that she had agreed to the plan.