There seems to be a lot of speculation here. How about a few concrete sources?
From the U.S. Department of Labor:
The Fair Labor Standards Act (FLSA) does not require payment for time not worked, such as vacations, sick leave or federal or other holidays. These benefits are matters of agreement between an employer and an employee (or the employee's representative).
From the Missouri Department of Labor & Industrial Relations:
Employers are not required to provide vacation pay, holiday pay, or severance pay — these are benefits given at an employer’s discretion. The exception would be instances where an employer has entered into a contract where certain benefits are established by agreement.
From the New York Department of Labor:
Q: Must an employer pay workers for holidays, sick time and/or vacations?
A: Under the New York State Labor Law, payment for time not actually worked is not required unless the employer has established a policy to grant such pay. Holidays, sick time and/or vacations fall under 'time not worked.' When an employer does decide to create a benefit policy, that employer is free to impose any conditions they choose.
From the California Department of Industrial Relations:
There is no legal requirement in California that an employer provide its employees with either paid or unpaid vacation time. However, if an employer does have an established policy, practice, or agreement to provide paid vacation, then certain restrictions are placed on the employer as to how it fulfills its obligation to provide vacation pay. Under California law, earned vacation time is considered wages, and vacation time is earned, or vests, as labor is performed. [...] And, unless otherwise stipulated by a collective bargaining agreement, upon termination of employment all earned and unused vacation must be paid to the employee at his or her final rate of pay.
- Illinois requires unused vacation to be paid.
- Nevada does not require it to be paid.
- Massachusetts says vacation is not required, but if offered, may be considered wages.
You can find most states' policies by searching for something like Missouri vacation laws.
As you see, the standards vary. The federal government doesn't require employers to pay vacation at all, but states may make more specific laws about it. In my personal experience, most employers do pay out unused vacation (except perhaps in the case of a firing), but the fact that they do so doesn't necessarily indicate that they're legally required to.
