Tax lien interest calculator
Most tax lien calculators multiply a rate by the time. Redemptions don't work that way. Florida pays a 5% minimum unless you bid zero, Iowa counts any part of a month as a month, Illinois counts six-month periods, and in Colorado the premium you bid is simply gone. This calculator applies the formula written in each state's statute, for the 23 states whose rules we have checked line by line, and shows every rule it used with a link to the law.
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How the calculator works
You enter what you paid, the rate you won where there is one, any premium or overbid, the purchase date and when you expect the owner to redeem. The calculator then applies the formula in that state's statute: what earns interest and what doesn't, how a part of a month is counted, whether there is a minimum, a flat penalty or a cap. Every line of the result names the rule and links to it.
Three numbers come out. Interest earned is what the redemption pays you on top of your money back. Total return is the net gain, after any premium the county keeps, divided by everything you put in. Annualized spreads that gain over the time each dollar was tied up, so a flat 25% that arrives in two months and 12% a year over two years can be compared.
Where the statute leaves a detail open, such as whether a yearly rate is counted by the day or by the month, the result says which convention we used. The county's own payoff figure is always the one that counts.
Worked examples
Calculated with the same code as the calculator. They illustrate the arithmetic; they are not forecasts of what any bid will return.
Florida: the 5% minimum, and the trap at 0%
A $2,000.00 certificate won at 0.5% on June 1, 2026 and redeemed on November 20, 2026 would earn only a few dollars at its bid rate. Because that is less than 5% of face, the owner pays the mandatory minimum: $100.00, a 5.0% return, or 10.6% a year over 172 days.
Bid the same certificate at 0% and the same redemption pays $0.00: the statute excludes zero-percent bids from the minimum (§ 197.472(2)). And if the owner instead waits until May 10, 2028, the 0.5% bid still earns only the 5% floor, $100.00, which is 2.6% a year. In Florida a low bid pays best on a quick redemption.
Florida tax liens in full →Iowa: 2% a month, counted generously
Iowa fixes the rate at 2% a month and counts each fraction of a month as a whole month, from the month of sale (Iowa Code § 447.1). A $1,500.00 certificate bought on June 15, 2026 and redeemed on April 10, 2027 covers 11 calendar months and pays $330.00, a 22.0% return, or 26.9% a year, a little above the headline 24% because the part-months round up.
Iowa tax liens in full →Colorado: when the premium eats the interest
Colorado pays the rate on the certificate, 13% for 2026 sales, but bidders compete with a premium that the county keeps (C.R.S. 39-11-115(1)). A $2,000.00 lien bought with a $400.00 premium on October 16, 2026 and redeemed on April 30, 2027 earns $151.67 in interest, but you put in $2,400.00: a net result of −$248.33.
Held until October 20, 2028, the same lien earns $541.67 and nets $141.67, which is 2.9% a year on the money you tied up. The premium decides whether a quick redemption is a loss.
Colorado tax liens in full →The rule we apply in each state
Each state page has the full statute and the exceptions. Rates are what the law allows; at auction they are often bid far lower.
Tax lien certificates (14)
Bid rate (18% cap) by the month, or a 5% minimum on face value, except on 0% bids.
Fla. Stat. § 197.172 · Fla. Stat. § 197.472(2) · Fla. Stat. § 197.432 · Volusia County Tax Collector, tax certificate FAQ
Bid rate (16% cap), simple, from the 1st of the month after purchase; part of a month counts as a month.
2% a month fixed, counted from the month of sale, any part of a month as a whole month.
Bid rate (18% cap) a year, plus a one-time 2%, 4% or 6% redemption penalty; the premium comes back without interest.
N.J.S.A. 54:5-32, 54:5-33 (DCA LFN 2010-7) · NJ DCA, Elements of Tax Sales (N.J.S.A. 54:5-61 penalty)
Penalty bid (9% cap) times each six-month period begun, up to six; later taxes 12% a year.
The certificate rate (13% for 2026 sales) from the sale date, part of a month as a month; the premium is lost.
C.R.S. 39-12-103 · C.R.S. 39-11-115(1) · Colorado Division of Banking, redemption rate notices
10% of the minimum bid within 6 months, 15% up to a year; the overbid earns 5% a year.
1.5% a month or part of a month on the price excluding surplus, from the 1st of the month after the sale.
The certificate rate (10% cap) on taxes and costs only; the overbid comes back without interest.
14% a year simple, fixed, from purchase to redemption; later taxes the same.
A one-time 3% plus 15% a year simple since the sale; later taxes 15% a year.
5/6 of 1% a month (10% a year) on what you paid for the assignment, and on later taxes.
No interest on your bid since 2022: if the owner redeems, you get the bid back and nothing more.
Redeemable deeds (9)
Flat 25% premium (50% in the second year on homesteads, farm land and mineral interests), not prorated.
Premium of 20% for the first year or part of it, plus 10% for each further year or part, on the whole bid.
Flat 15% of the purchase price if the owner redeems within 60 days of the court approving the sale.
Lump 3%, 6%, 9% or 12% of the whole bid by quarter of the redemption year, capped at the opening bid.
18% a year on the total purchase price from the sale; 6 months to redeem (60 days if abandoned).
12% a year on the entire purchase price, from the day you paid until the motion to redeem.
10% of the price within 6 months, plus 1% of the price for each month after; intervening taxes 1% a month.
1.5% a month on taxes and costs, any fraction of a month as a month; the overbid is kept by the county.
Not yet supported
We only add a state when its formula is in a statute we have read. These are left out, and why:
Each county sets the rate (6% by default, 20% in Montgomery and Prince George’s, 10% at most on owner-occupied homes) and treats the high-bid premium its own way. It needs a county table first.
Each county chooses every year between a lien auction (12%, bid down) and a sale of the property (8% on the price, with limits on the excess bid). The two pay differently.
New system since January 1, 2026. The 5% penalty runs on the tax part of the certificate only, and how part-months are counted isn’t settled in our sources yet.
Only some counties sell certificates, and auction sales and negotiated bulk sales follow different rules (R.C. 5721.32, 5721.33).
A county may sell certificates only if its commissioners waive the statutory ban (SDCL 10-23-28.1), so there is rarely anything to buy.
Each county writes its own tax sale code. We have checked Honolulu’s and Hawai‘i County’s, not Maui’s or Kaua‘i’s.
No statewide lien sale: Nassau County auctions liens under its own law and New York City sells only to a trust.
The town takes the tax title and only sometimes assigns it; the rate depends on the taking date (8% or 16%).
The town keeps the lien; private buyers get one only where the town votes to auction it.
No lien sale to investors: the town’s own lien forecloses after 18 months.
Nothing to calculate in 18 tax deed states, where the property itself is sold with no redemption after the sale and no interest is paid to the buyer:Alaska, Arkansas, California, Idaho, Kansas, Michigan, Minnesota, Nevada, New Mexico, North Carolina, North Dakota, Oklahoma, Oregon, Pennsylvania, Utah, Virginia, Washington, Wisconsin.
Quick answers
How is tax lien interest calculated?+
It depends on the state, and the differences are bigger than the rates. Florida and Arizona charge a yearly rate by the month. Iowa charges 2% for every month or part of a month. Illinois charges your penalty bid once for each six-month period that has begun. Texas and Georgia pay a flat premium that does not grow with time, and South Carolina pays a lump 3% to 12% by quarter. This calculator applies each formula as the statute writes it.
What is Florida's 5% minimum on tax certificates?+
When a Florida certificate is redeemed and the interest at the bid rate comes to less than 5% of the face amount, the owner pays a mandatory minimum of 5% of face instead (Fla. Stat. § 197.472(2)). It applies to every certificate except those bid at 0%, which earn nothing at all. That is why a 0.25% bid and a 0% bid are very different investments.
Do I get my premium or overbid back?+
In New Jersey, D.C. and Missouri it comes back with no interest; in Indiana it comes back with 5% a year. In Colorado and Mississippi the county keeps it, so it is a straight loss, and the calculator shows it as one. In redeemable deed states like Georgia, Texas, Tennessee and Vermont the premium or interest runs on your whole bid, while South Carolina caps it at the opening bid.
How is the annualized return worked out?+
Net gain divided by the money you had tied up, weighted by how long each dollar was in: the lien from the purchase date, later taxes from the day you paid them. It is simple, not compounded. A flat premium redeemed in a few weeks gives a very high annualized figure, which says nothing about whether the next one will redeem that fast.
Does the calculator include fees?+
No. Certificate, processing, recording, redemption and attorney fees vary by county and are left out, as are the costs of a deed application or foreclosure. If a fee is repaid to you on redemption, you can add it to the amount you enter.
What happens if the owner never redeems?+
Then none of these numbers are paid. You move to the deed or foreclosure stage, which costs money and time, and you may end up with a property, a share of one, or a refund. Many liens on unwanted parcels are never redeemed. The calculator shows what a redemption would pay, never what you will earn.
Want the date instead of the dollars? The redemption tracker estimates when a state's window closes, and My Liens keeps the ones you bought. To compare states before you bid, see the tax lien rates by state, ranked.
This calculator is informational, not financial, legal or investment advice, and it promises no return. It shows what the statute says a redemption would pay on the numbers you enter. Real dates, amounts, fees and payoffs are set by the county, rules can change, and the owner may never redeem, in which case none of this is paid. Always confirm with the county before you bid.