Here's a list from 2012 of states with PTO/vacation payout laws at termination/separation (or lack thereof), check your state's labor department for updated regs (or your company's policy/your contract). USUALLY this type of law will preclude any "use it or lose it" provisions (as this defines vacation as a earned compensation), but again, check your local laws.
Source:
http://www.businessmanagementdaily.com/30895/state-laws-on-vacation-pay-after-termination#_
ALABAMA
No law
ALASKA
Payments agreed to, including unused vacation, must be paid
ARIZONA
Unused vacation must be paid if employer policy is to pay
ARKANSAS
Payment depends on employer contract
CALIFORNIA
Accrued vacation pay must be paid
COLORADO
In accordance with any agreement, accrued vacation pay must be paid
CONNECTICUT
Unused vacation must be paid if employer policy is to pay
DELAWARE
Benefits or wage supplements include vacation pay
DISTRICT OF COLUMBIA
Unused vacation must be paid if employer policy is to pay
FLORIDA
No law
GEORGIA
No law
HAWAII
Unused vacation must be paid if employer policy is to pay
IDAHO
Accrued vacation pay must be paid
ILLINOIS
Accrued vacation pay must be paid
INDIANA
No law
IOWA
Unused vacation must be paid if employer policy is to pay
KANSAS
No law
KENTUCKY
Unused vacation must be paid if employer policy is to pay
LOUISIANA
Unused vacation must be paid if employer policy is to pay
MAINE
Accrued vacation pay must be paid
MARYLAND
Accrued vacation must be paid, if employer has no vacation policy
MASSACHUSETTS
Unused vacation must be paid if promised under oral or written agreement
MICHIGAN
Unused vacation must be paid according to written contract or policy
MINNESOTA
Unused vacation must be paid according to written contract or policy
MISSISSIPPI
No law
MISSOURI
Unused vacation must be paid according to written contract or policy
MONTANA
Accrued vacation pay must be paid
NEBRASKA
Accrued vacation pay must be paid
NEVADA
No law
NEW HAMPSHIRE
Unused vacation must be paid if employer policy is to pay
NEW JERSEY
Unused vacation must be paid if employer policy is to pay
NEW MEXICO
No law
NEW YORK
Unused vacation must be paid if employer policy is to pay
NORTH CAROLINA
Unused vacation must be paid if employer policy is to pay
NORTH DAKOTA
Accrued vacation pay must be paid if employee worked for at least one year
OHIO
Unused vacation must be paid if employer policy is to pay
OKLAHOMA
In general, accrued vacation pay must be paid
OREGON
Unused vacation must be paid if employer policy is to pay
PENNSYLVANIA
Unused vacation must be paid if employer policy is to pay
RHODE ISLAND
Accrued vacation pay must be paid if employee worked for at least one year
SOUTH CAROLINA
Accrued vacation must be paid
SOUTH DAKOTA
No law
TENNESSEE
Unused vacation must be paid if employer policy is to pay
TEXAS
Unused vacation must be paid if employer policy is to pay
UTAH
Unused vacation must be paid if employer policy is to pay
VERMONT
Unused vacation must be paid if employer policy is to pay
VIRGINIA
No law
WASHINGTON
No law
WEST VIRGINIA
Unused vacation must be paid if employer policy is to pay
WISCONSIN
Unused vacation must be paid if employer policy is to pay
WYOMING
No law
