or would you suggest coding every loan that is a non-natural person with the NA?
As hmdadal stated every loan to a non-natural person the income should be reported NA. You don't have an option. Income reported on a non-natural person would be a reporting error on the LAR.
What if you have two applicants / borrowers - one is a non-natural person and one is a natural person.
That's a good question. My opinion is;
If the loan is made to a natural person jointly with a non-natural person and the natural person's income was used in the credit decision then you report their income. I'm basing this primarily on the following:
. . . Similarly, if an institution relies on the income of a cosigner to evaluate creditworthiness, the institution includes this income to the extent relied upon. . . .