If It's a Loan, Don't Pretend It's a Gift
Is it immoral to lend money but, for tax purposes, to sign a letter stating that it was a gift?
It sounds like you’re trying to have it both ways. That is, you apparently want your money to be paid back to you, and yet legally you’ve signed—or are considering signing—a letter that says it’s a gift, so that you can gain a tax benefit too, as well as perhaps the loan recipient or some other party gaining additional benefit. If that’s correct, that would be immoral, because you’d be getting a tax benefit for a gift you didn’t make. You either need to make a loan or give a gift for which you can get a tax credit. You legally and morally can’t do both.
If you can’t afford to give a gift, then make it a legally binding loan. Or make a loan and forego receiving a tax credit for the gift. In doing so, you’ll do the right thing and have the peace of mind that goes with it (see John 14:27).