I keep seeing accessibility as a separate line item in proposals and that's wrong. I won't stop insisting, sorry.
It's not just moral, it's practical. A user whose mouse isn't working can't fill out a form that can't be navigated by keyboard. No one can see a low-contrast button on a phone in sunlight. These aren't edge cases, they happen to everyone.
Minimum list: every form field should have a label, focus should be visible, text contrast should be sufficient, don't convey info by color alone, respect reduced motion preferences.
None of these are expensive, adding them later is. If considered during the design phase, the cost is near zero.