The City of Boulder published the interest rate for 2021 tenant security deposits.  It is set at 0.07%, effective Friday, Jan. 1, 2021. This is the mathematical average of the one-year certificate of deposit from the top three financial institutions in Boulder, based on market share data as of Dec. 14, 2020. The tenant security deposit interest rate is recalculated each year in accordance with Ordinance 7320, which was adopted on Feb. 17, 2004. Relevant code language may be found in Chapter 12-2: Landlord-Tenant Relations of the Boulder Revised Code (sections 12-2-2 and 12-2-4 through 12-2-7).  The rate is the average of the one-year certificate of deposit from the top three financial institutions in Boulder, based on market share data as of Dec. 15, 2018. The computation formula of the interest due for residential security deposits in the City of Boulder is:  Multiply the entire amount of the security deposit by the appropriate multiplier for that year, divide that number by 12 to obtain a monthly percentage amount due, and then multiply that monthly number by the number of months the deposit was in the landlord’s possession, including the 30 or 60 days after the end of the lease. The rate in effect at lease signing is in effect for that lease period, until termination or renewal for another period.  Month to month leases are considered renewed each month, so the interest rate due will change on the first of every calendar year for month to month leases. Click Here to View Security Deposit Interest Rates for City of Boulder.