It depends on your employer and where you live. 24 states—Alaska, Arizona, California, Colorado, Illinois, Indiana, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Minnesota, Nebraska, New Hampshire, New York, North Carolina, North Dakota, Ohio, Oklahoma, Pennsylvania, Rhode Island (after one year of employment), Tennessee, West Virginia, and Wyoming—and the District of Columbia have laws regarding payment of accrued vacation time. However, in those states, you are only given a legal right to challenge an employer over unpaid accrued vacation time in your final paycheck if the employer has promised payment of unpaid accrued vacation time in your final paycheck. In the rest of the states, there is no state law that requires your employer to pay you for accrued vacation leave, although your employer may do so voluntarily, or may have to do so if required by a policy or contract.
Unless required to do so under an employment contract, collective bargaining agreement, or other legally binding agreement, an employer is not required to pay employees for accrued sick time or personal leave when they leave their employment. In this respect, accrued sick time is unlike accrued vacation time which, in some states, must be paid as part of an employee's final paycheck. Some employers do pay employees for unused sick time, possibly as an incentive for employees to not misuse sick leave. However, this practice is generally completely voluntary, unless required by a contract as discussed above.
More companies are moving to a paid time off (PTO) system where days off are not designated as vacation leave, sick leave, or personal leave, to give employees more flexibility and to ease the administrative burden of tracking and policing workers' use of their time off. Where this is the case, remaining PTO days are generally treated the same as vacation days under the law. These days are considered to be accrued by the employee and payable when the employee leaves the job.