Try this
- If the recipient asks how to repay you and you do not need repayment, say that plainly.
- If there was a practical agreement about costs or tasks, clarify it separately from the personal gesture.
A worked example
“There is nothing you need to do in return for the note. The train cost we agreed to split is a separate practical thing.”
An invented example to adapt, not a real exchange or a script you have to follow.
Before you leave it here
Avoid later invoking a supposedly no-strings gesture as leverage. If you expect an exchange, state that before the action so the other person can choose.