2021 UnitedHealthcare Administrative Guide
“You must submit both your reconsideration and appeal to us within 12 months (or as required by law or your Agreement), from the date of the EOB or PRA. The 2-step process, as outlined below, allows for a total of 12 months for timely submission for both steps (Step 1: Reconsideration and Step 2: Appeals).”
To view the full Claim Reconsideration and Appeal process, forms, instructions, and etc. for UHC follow this LINK.