Notify Colorado Secretary of State
The Secretary of State requires that in order to withdraw your registration with the state, you will need to file any final forms including the final renewal (which is due the 15th of the 5th month after the close of your fiscal year). After these filing are complete, you must file Articles of Dissolution.
Notify the IRS
In addition to letting the state know, you will also need to let the IRS know. In publication 4779, the IRS explains how to terminate or merge your organization step by step. You will typically inform the IRS by filing a final Form 990, 990-EZ or 990-N.
Smaller organizations may submit a Pro Bono Legal Request to receive legal assistance for the dissolution process.