Hey there!

I got a donation for one of my fonts for commercial use. The donor now want a written permission.
Honestly I never thought of that and I have no idea how to write this.

Is it enough to write a letter in business style and write that I give that person permission to use the font for commercial purpose? Do I have to say that the permission isn't transferable or something like that?

Please help me, thank you

I've got so far

"I, (Name), hereby give permission for (Name), to use my font (Name) for commercial purpose for a donation of 10$."

Is this ok?

Byjanam, there is no need to make it very formal or legal. As long as there can be no doubt that you have received a donation and that you grant permission for use as described in the reason for donating.

Dear (Full Name),

Thank you for your interest in my font (FontName) and your US $10.00 donation for the use for (Description of Use).
You now have my permission to use the (FontName) for this purpose. This permission, however, is not a transfer of copyright and does not imply a right to transfer your right of use.

I wish you success with the use of the (FontName).

Kind Regards.
(Your FullName)

PS: Be nice to the cats

The donor now want a written permission.

If you want something formal, you can try to inspire you with publishing licenses, simplifying it.
It's aesy to find some templates on Internet (sorry, I know adresses only in french).