Cobb County Property Tax: Rates, Exemptions, and Appeals

Property owners in unincorporated Cobb County pay a combined 30.13 mills in property tax for 2025, applied to 40% of the home’s fair market value. Bills go out by August 15 and must be paid by October 15. The 30.13-mill rate covers county government, the Cobb County School District, and fire protection; if your home sits inside a city, the mix shifts. Rates for 2026 won’t be set until late July or early August, when local taxing authorities approve them.

What the 2025 Millage Rate Actually Covers

One mill equals $1 of tax per $1,000 of assessed value. The 30.13-mill total for unincorporated Cobb breaks down this way:

County general government: 8.46 mills
Cobb County School District: 18.70 mills
County fire district: 2.97 mills

That combined rate applies to properties outside any city limits.¹

City Rates

Properties inside a city pay the city’s millage in addition to applicable county levies. The 2025 municipal general rates are:

Acworth: 8.95 mills
Austell: 8.25 mills
Kennesaw: 7.75 mills, plus a 1.40-mill bond levy
Marietta: 2.867 mills, plus a 1.825-mill city bond levy and 17.97 mills for the Marietta Independent School District, which replaces the county school levy
Powder Springs: 9.50 mills
Smyrna: 8.99 mills

Marietta runs its own school system, so residents there pay the Marietta school millage instead of the Cobb County school rate. Certain commercial improvement districts within Marietta carry an additional levy.¹

How Your Bill Is Calculated

The Cobb County Board of Tax Assessors sets the fair market value of every property as of January 1 each year.² Georgia then taxes you on 40% of that value. The 40% figure is your assessed value, and it’s the base for all the math.³ A $400,000 home has an assessed value of $160,000. A $600,000 home sits at $240,000.

Here’s how a bill shakes out on that $400,000 home in unincorporated Cobb at the 2025 rate:

Fair market value: $400,000
Assessed value (40%): $160,000
Minus the $10,000 basic homestead exemption: $150,000 net assessed value
Apply millage: $150,000 × 30.13 ÷ 1,000 = $4,519.50

Multiplying net assessed value by the millage rate and dividing by 1,000 converts mills into dollars.⁴ For properties inside a city, swap in the applicable municipal and school rates; the formula is the same.

Exemptions That Lower Your Bill

Exemptions reduce your assessed value before the millage is applied. To qualify, you must own and occupy the property as your primary residence on January 1 of the tax year.⁵ Cobb County’s main tiers:

Basic homestead: $10,000 off in the county general and school general categories. Every owner-occupant qualifies.
Age 62 school tax exemption: removes all school general and school bond taxes for homeowners 62 or older by January 1. Proof of age required.
Age 65 state senior exemption: $4,000 off in the state, county bond, and fire district categories, if income doesn’t exceed $10,000 (excluding certain retirement income).
Disability exemption: $22,000 off in all categories except state.

You apply through the Tax Commissioner’s office.⁶

Veterans and Surviving Spouses

Disabled veterans rated 100% by the VA, or receiving benefits at the 100% rate due to unemployability, qualify for a homestead exemption of up to $50,000 against all ad valorem taxes. The exemption passes to an unremarried surviving spouse or to minor children who continue living in the home.⁷ A separate exemption of up to $50,000 covers the unremarried surviving spouse of a service member killed in any war or armed conflict.⁸ Cobb County also recognizes a full-value homestead exemption for the surviving spouse of a peace officer or firefighter killed in the line of duty, which wipes out the entire assessed value.⁶

Paying the Bill

Cobb County mails tax bills by August 15 each year, and payment is due by October 15. Mailed payments must be postmarked by that date.² You have several options:

Online: e-checks carry no convenience fee; Visa, Mastercard, Discover, American Express, and PayPal are accepted with a convenience fee.
By mail: send a check or money order to the Tax Commissioner’s office.
In person: the Property Tax Division at 736 Whitlock Ave in Marietta, the East Cobb Office at 4400 Lower Roswell Rd, or the South Cobb Government Service Center at 4700 Austell Rd.
By phone: call 1-866-PAY-COBB (1-866-729-2622) for the automated system. Processing fees depend on payment method.

Once your payment clears, the office issues a receipt that serves as proof for mortgage lenders and title companies.²

What Happens If You Pay Late

Missing the October 15 deadline triggers an immediate 5% penalty on the unpaid amount.⁹ If the balance stays unpaid, Georgia law adds another 5% penalty at each 120-day interval, with total penalties capped at 20% of the original tax. Interest also accrues at 1% per month on amounts over $1,000, up to 12% per year.¹⁰

Once taxes go delinquent, the Tax Commissioner can issue a tax execution, which is a lien against the property. If the debt remains unresolved, the property is placed on a tax sale list. The county advertises these properties in the Marietta Daily Journal for four consecutive weeks before the sale and posts the list on the Tax Commissioner’s website.¹¹

Redeeming Property After a Tax Sale

Georgia gives the original owner up to 12 months from the sale date to reclaim the property, but the cost climbs fast. You repay the full tax sale purchase price, any taxes the buyer paid afterward, and a 20% premium if you redeem within the first year. After that, an additional 10% premium accrues for each year or partial year.¹² Wait more than 30 days after the buyer sends a formal redemption notice and you also owe the sheriff’s service costs and any publication fees. At that point, the redemption right can be foreclosed entirely.¹³

Appealing Your Assessment

The Board of Tax Assessors must mail an annual notice of assessment by July 1, showing the current fair market value, assessed value, and the previous year’s figures.¹⁴ If you think the value is too high, you have 45 days from the notice’s mailing date to file a written appeal with the Board of Tax Assessors.¹⁵ Georgia law allows three grounds:

Value: a knowledgeable buyer wouldn’t pay that much in an arm’s-length transaction.
Uniformity: your property is assessed higher than comparable ones.
Taxability: the property shouldn’t be taxed at all, or a portion qualifies for an exemption that wasn’t applied.

A written objection identifying the property and stating your disagreement counts as a valid appeal. Once filed, the Board of Equalization schedules a hearing within 15 days and holds it within 30 days of notifying you, announcing its decision at the hearing’s close.¹⁶ The 45-day clock runs from the mailing date on the notice, not the day you open it, so mark your calendar as soon as it arrives.

1
Cobb County Tax Commissioner. 2025 Millage Rates
2
Cobb County Tax Commissioner. Cobb County Tax Commissioner Property Overview
3
Justia. Georgia Code 48-5-7 – Assessment of Tangible Property
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Department of Revenue. Property Tax Millage Rates
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Justia. Georgia Code 48-5-40 – Definitions
6
Cobb County Tax Commissioner. Cobb County Homestead Exemptions
7
FindLaw. Georgia Code Title 48 Revenue and Taxation 48-5-48 – Disabled Veteran Homestead Tax Exemption
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FindLaw. Georgia Code Title 48 Revenue and Taxation 48-5-52.1 – Homestead Exemption for Surviving Spouse of Armed Forces Member
9
Justia. Georgia Code 48-5-24 – Payment of Taxes to County
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Justia. Georgia Code 48-2-44 – Failure to Pay Ad Valorem Tax
11
Cobb County Tax Commissioner. Tax Sales
12
Justia. Georgia Code 48-4-42 – Amount Payable for Redemption
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Justia. Georgia Code 48-4-40 – Persons Entitled to Redeem Land Sold Under Tax Execution
14
Justia. Georgia Code 48-5-306 – Annual Notice of Current Assessment to Taxpayer
15
Georgia Department of Revenue. PT-311A Appeal of Assessment Form
16
FindLaw. Georgia Code Title 48 Revenue and Taxation 48-5-311 – Assessment Appeal Process