As often happens when new laws are enacted in Costa Rica (and, I am sure, elsewhere in the world), there is a lot of confusion about the details. The issue of new “mandatory” license plates is no exception. The Tico Times recently published an article that explains that the new plates are NOT mandatory yet and the the process of converting over to the new plates begins this April but will be implemented over the next three years. So don’t panic, especially if you have an older model car, as new cars will be the first to be issued new plates. Here’s a link to the story: Rumors swirl around new license plate rules.
And here is link to more information on the Lake Arenal Forum: Mandatory New License Plates.