Emerald Club members can earn a free car rental through National Car Rental’s annual “One Two Free” promotion running through Jan. 31, 2015. Emerald Club members who register for the promotion will get one free rental day for every two qualifying rentals of two or more days. In order to qualify, the rental must also be a mid-size or larger vehicle rented from participating locations in the United States.

Members can earn up to 50 free rental days during the promotion that they can use for up to three free days per rental, along with other offers for additional bonus points. Members can earn a one-time bonus of 300 points upon renting any size vehicle in Mexico, a one-time bonus of 250 points upon adding a GPS to a car rental and a one-time bonus of 250 points when adding the fuel service option to a car rental. You can refer up to 10 friends to join the Emerald Club and you will get 300 points per individual who signs up and completes a rental in the “One Two Free” promotion by Jan. 31, 2015.

Downloading the National mobile app will net you a one-time 25 points bonus while connecting to National’s “One Two Free” promotion site via Facebook will get you a one-time bonus of 50 points. And if you participate in the Emerald Reserve service, reserving a specific car class like a convertible, SUV, minivan, at Emerald Aisle locations, you’ll earn a one-time bonus of 25 points.

Each qualifying car rental completed during the “One Two Free” promotion is worth 300 points, with a free day awarded once an Emerald Club member earns 600 points. Members get 300 points for every qualifying rental or 300 points for every four consecutive days, so if you rent for eight days, you’ll get 600 points and if you rent for 24 days you would get 1,800 points. The free days earned through the “One Two Free” promotion are awarded in addition to frequent travel miles/points or rental credits.

Emerald Club members must register for the promotion at http://www.emeraldclub.com/Free You can follow your “One Two Free” status at this link to see your point balance and activity as well as the points available for redemption. When your points total reaches 600, you will automatically get a free rental day coupon that is valid until June 15, 2015.

Bottom line: This can be a lucrative promotion if you frequently rent cars with National. You have until the end of January to earn up to 50 free rentals, can redeem up to three free rental days per booking and have until the middle of June to spend your free rental coupons.