UFAS

Any project that involves federal funding must comply with UFAS. This means direct funding, block grants, vouchers, the whole nine. All tax credit financed projects which take vouchers must comply with UFAS. The short answer here is that 5% of the units must comply with UFAS standards, regardless of the local jurisdiction's requirements (which, depending on where you are, requires 2% to 15% of units to be accessible per the IBC, which references ANSI 117.1).

It seems that in jurisdictions that require less than 5% accessible units, the compliance with UFAS (5%) is a safe harbor.

In jurisdictions that require more than 5% accessible units, compliance with UFAS for the 5% and compliance with ANSI for the remaining required units would suffice. Or UFAS for all of them.

When there is no federal money involved, UFAS doesn't apply.

Quick access to the Uniform Federal Accessibility Standards.

And the mother of all checklists for UFAS is here.