The short answer to that question is : Yes, you do have to register your ATV and any Off-Highway Vehicle for that matter. It is a State Regulation that is absolutely enforced. Don't get caught riding without a registration, the ticket isn't worth it compared to the small cost of registration.
In order to register your ATV in Delaware, you must go in person to the Division of Motor Vehicles office. Then all you have to do is provide a description of your ATV which includes make, year and serial number and you must be at least 18 years of age unless you have at least one parent or legal guardian who provides written consent on the application and accompanies you to the Division of Motor Vehicles Office. The fee for registration is $6.00 for three years. You may pay via cash or check, credit cards are not accepted.
Further Delaware regulation that you should know state that ATVs may not be operated on public streets or highways, and the rider must have the permission of the property owner before operation on private property.
A helmet is also required by law no matter what the age of the ATV rider. This includes all ATV operators and passengers. The ATV helmet must be completely in place with the chinstrap fastened.
Delaware also requires that all ATVs have a braking system installed and a muffler in place that reduced the noise levels of the vehicle by up to 60-percent. Spark arrestors are required if you are riding your ATV on federally managed lands to reduce the chance of forest fire.
Now that you know the rules and regs for riding your ATV in Delaware, get out there and have a great time!