Changing contribution financial type from non-deductible to deductible does not change non-deductible amount, resulting in inability to issue tax receipts
Suppose someone enters a donation with an event fee financial type by mistake. The non-deductible amount is set to the full amount of the contribution. If they then change the financial type to a donation type, the non-deductible amount remains the full amount of the contribution, so no tax receipt can be issued for the donation. Since most people probably don't use non-deductible amount regularly, if at all, they aren't likely to check this. Not a big deal if you then try to issue a tax receipt for the single contribution as it will be obvious that something is wrong (though perhaps frustrating because it isn't clear what), but if you are issuing them in bulk, you may not notice this at all, resulting in a donor not getting their tax receipt — a pretty bad outcome from a donor stewardship perspective.
We probably don't want to change non-deductible amounts in the background for existing contributions, but how about a warning that pops up when the financial type is changed from non-deductible to deductible, advising the user to check the non-deductible amount? Perhaps this wouldn't matter to some users, who don't care at all about deductible versus non-deductible, but this does seem worth warning about because it can produce unexpected results in the background.
Something like:
You've changed the financial type for this $NNN contribution from non-tax deductible to tax deductible, but the non-deductible amount of $NNN has not been changed. This could prevent a tax receipt from being issued. You may want to edit the non-deductible amount.