What is a Letter ID - from CO website: "When you receive correspondence regarding your taxes from the Colorado Department of Revenue, the letter contains a "Letter ID" in the upper right corner of the document. The ID number starts with the letter "L." You may use the Letter ID as a security key to set up access to your account in Revenue Online"
However, if you know your refund amount, then you do not need a letter ID. The website allows you to track your refund with just SSN and refund amount.
https://www.colorado.gov/revenueonline/
If you do not know the refund amount you claimed, then "you may either use a Letter ID number from a recent income tax correspondence from the Department, or you may request a letter with a Letter ID be sent to you to the mailing address we have on file for you. You will receive the Letter ID within 7-10 business days"
There is an option at the bottom of the homepage of the link above that will allow you to request a Letter ID.
