Security Deposit Interest Calculator CT
Use this Connecticut security deposit interest calculator to estimate interest owed on a residential rental security deposit under Connecticut General Statutes Section 47a-21. The calculator applies year-by-year statutory rates, so it is more accurate than a single average-rate calculator for multi-year tenancies.
Calculate CT Security Deposit Interest
Year-by-Year Calculation Breakdown
| Year | Rate | Days Applied | Starting Balance | Interest | Ending Balance |
|---|
Connecticut Security Deposit Interest Rates
The Connecticut Banking Commissioner publishes the deposit index used to determine the minimum interest rate for residential rental security deposits. For calendar year 2026, this calculator uses 0.49 percent. For 2025 it uses 0.52 percent, and for 2024 it uses 0.55 percent.
| Calendar year | Rental security deposit rate used by this calculator |
|---|
Tip: If your lease period includes years before this table begins, switch to manual rate mode or add those historical rates in the JavaScript rate table.
How the Calculator Works
This tool calculates interest by splitting the tenancy into calendar-year segments. Each segment uses the rate for that calendar year and the exact number of days the deposit was held during that year.
Base formula
Interest equals deposit balance multiplied by annual rate multiplied by days held divided by days in that year.
Using days in the actual calendar year improves accuracy for leap years, such as 2024.
Annual compounding option
Connecticut law defines accrued interest as interest due under the statute and can involve annual compounding to the extent applicable. The calculator includes an annual compounding checkbox so users can model that approach transparently.
Practical Examples
Example 1: One-year lease in 2026
A tenant pays a 2,000 dollar security deposit on January 1, 2026 and moves out on December 31, 2026. At a 0.49 percent annual rate, the estimated interest is about 9.79 dollars when calculated through December 31, or about 9.80 dollars for a full 365-day period depending on date convention.
Example 2: Multi-year tenancy
A deposit held from January 1, 2024 through May 5, 2026 should not use one blended guess if official rates are available. This calculator allocates days to 2024, 2025, and 2026 separately, then adds the interest from each segment.
Example 3: Late-rent adjustment
If certain months are excluded because rent was late beyond the statutory grace period, enter the number of excluded months. The calculator subtracts an approximate month-equivalent from the total applied days, starting from the most recent segment. For a formal legal claim, verify the exact months and statute application with a qualified professional.
Key Connecticut Security Deposit Rules
Interest payment timing
Landlords generally must pay or credit security deposit interest annually on the anniversary of the tenancy, or pay the accrued amount when the tenancy ends.
Return deadline
Connecticut security deposit rules include strict return timing. In many common cases, the landlord must return the deposit balance with required interest within 30 days after the tenant vacates or within 15 days after receiving a forwarding address, whichever is later.
Deposit limit
For many residential tenants, Connecticut caps the amount of security deposit a landlord may demand. The cap is commonly two months rent, and one month rent for tenants age 62 or older. Verify the current statute for exceptions and exact wording.
Allowed deductions
Interest is separate from lawful deductions. A landlord may still claim valid deductions for unpaid rent or damages beyond ordinary wear and tear, but should document deductions clearly.
Frequently Asked Questions
Is security deposit interest required in Connecticut?
Yes. Connecticut residential landlords generally must pay tenants interest on security deposits at the rate determined annually by the Banking Commissioner.
What is the CT security deposit interest rate for 2026?
The rate used in this calculator for 2026 is 0.49 percent.
Why is this better than a simple average-rate calculator?
A single average rate can be wrong when the lease spans multiple years. This tool splits the period by calendar year and applies the correct rate to each segment.
Does the calculator handle leap years?
Yes. The script uses 366 days for leap years and 365 days for other years.
Can I use this result in court?
You can use it as an estimate and documentation aid, but you should verify official rates, exact dates, rent-payment history, deductions, and legal requirements before relying on it in a dispute.
Suggested Internal Links
Replace these sample URLs with your real site URLs to improve topical authority and user navigation.
Sources to Verify
- Connecticut Department of Banking rental security deposits page.
- Connecticut Department of Banking annual deposit index memoranda.
- Connecticut General Statutes Section 47a-21.