As a salaried employee who also earns a bonus, is the company supposed to pay vacation time on bonuses earned?

I am entitled to 4 weeks’ vacation annually but only ever takes about 1; is the company supposed to pay for unused vacation time when I retire/resign?

Generally, the company should be paying vacation on the bonus. In terms of vacation, it depends on the company's policy as they could ave a policy that forfeits any unused vacation time above your minimum entitlement (2 weeks of vacation, 3 weeks after 5 years). If they dont have this type of policy then they would have to pay it out to you or force you to use your vacation.