Renewal of a non active LLC
How do a renew a LLC, which has not been active in several years?
The answer would greately depend on the state of formation. Many states would administratively dissolve your LLC for failing to pay whatever annual fees or taxes this state has for LLCs, with or without the option to reinstate the company. If that is the case, you would probably need to simply register a new LLC.
There are some exceptions, for example New Mexico LLCs have no annual fee, so LLCs in that state would never get administratively dissolved. Again, to give you a meaningful answer I would need to know more details about the company, such as name and state of registration.