An estimated 33% of Cobb County homes were overvalued in 2025, and the county opted out of HB 581's tax cap at every level. Here is what your notice means, how to check your value, and how to file an appeal before the 45-day deadline.
# Your Cobb County 2026 Assessment Notice Explained
Cobb County assessment notices are expected to arrive in mid-to-late May 2026, and the numbers on them deserve careful attention. An estimated 33% of Cobb County homes were overvalued in 2025. Only 32% of residential properties were reassessed that year, but those that were saw a median increase of 8.59% (with an average jump of 20.49%). The county's overall tax digest growth slowed to 3.1%, down from 8.5% in 2024 and 13% in 2023, yet that headline figure masks the sharp increases concentrated on reassessed properties. Making matters worse, Cobb County opted out of HB 581's floating homestead exemption at every level. The county commission voted 4-0 against it, and the school district, Marietta, and all other cities followed suit. The county's existing floating homestead exemption provides some protection, but it does not cap assessed value increases the way HB 581 would have. With school taxes at 18.70 mills representing roughly 62% of the typical tax bill, even a modest overvaluation translates to real money.
Georgia law requires all property to be assessed at 40% of its fair market value. Your county does not tax you on what your home is worth. It taxes you on 40% of that number, called the assessed value.
If your county says your home is worth $400,000, your assessed value is $160,000. That $160,000 is what the millage rate applies to when calculating your tax bill.
This ratio is set by state statute (O.C.G.A. 48-5-7) and applies uniformly across all 159 Georgia counties. It has been the standard for decades and is not subject to annual change. A handful of cities assess at different ratios (Dalton and Gainesville at 100%, Decatur at 50%), but these exceptions are rare and do not affect county-level assessments.
The 40% ratio has a practical consequence for appeals: every $10,000 your home is overvalued translates to $4,000 in excess assessed value. That may look small on paper, but at a typical Georgia millage rate of 30-40 mills, it adds $120-$160 to your annual tax bill, and compounds over multiple years.
Your Annual Notice of Assessment arrives by mail (and increasingly online) from your county Board of Tax Assessors. It is not a tax bill. It is the county's estimate of your property's fair market value as of January 1 of the current year.
The notice shows three key numbers:
The notice also prints the date it was issued. That date starts your 45-day appeal clock. If you believe the FMV is higher than what your home would actually sell for, you have the right to challenge it. You are not appealing your tax bill or the millage rate, only the county's estimate of your home's market value.
Check the property details on the notice carefully. Errors in square footage, lot size, bedroom/bathroom count, or condition rating are common and can inflate your assessed value. The National Taxpayers Union Foundation found that incorrect square footage appears in 18% of assessments.
Before filing an appeal, run a quick sanity check to see whether your assessment is actually too high:
You can also check the assessor's property card for errors. Look for incorrect square footage, wrong lot size, inaccurate bedroom/bathroom count, or a condition rating that does not match your home. These errors are more common than you might think. The National Taxpayers Union Foundation found that 30-60% of U.S. properties are overassessed, yet fewer than 5% of homeowners file an appeal.
Georgia law gives you exactly 45 days from the date on your Notice of Assessment to file a written appeal. This deadline is strictly enforced. Even one day late means you forfeit the right to appeal for the entire tax year.
The deadline is not 45 days from when you receive the notice. It is 45 days from the date printed on the notice itself. Mail delays are common, especially in metro Atlanta, so do not wait for the paper notice to arrive. Most counties post notices online before the paper version reaches your mailbox.
If your notice is dated June 15, your deadline is July 30. If it is dated May 1, your deadline is June 15. Count the days carefully, and file early to avoid any last-minute issues with online portals or postal service delays.
You can file by mail (postmark date counts), online through your county assessor's portal, or in person at the assessor's office. For mail filings, use certified mail or USPS statutory overnight delivery so you have proof of your filing date.
Cobb County has mailed assessment notices in May for the past three years: around May 15 in 2023, around May 10 in 2024, and May 23 in 2025. For 2026, expect notices in mid-to-late May with a deadline falling in early-to-mid July. Check assessor.cobbcounty.gov for your notice as soon as assessment season begins. Online notices are typically available before the paper version arrives.
After notices are mailed, the Board of Tax Assessors holds help sessions at four library locations: East Cobb Library, Mountain View Regional Library, Kemp Memorial Library, and South Cobb Regional Library. These sessions are a good resource if you have questions about your notice or the appeal process. Dates and times are posted on the assessor's website once the schedule is finalized.
You have three ways to file. All three are equally valid.
File through the Cobb County Board of Tax Assessors portal at assessor.cobbcounty.gov/appeals. Search for your property by owner name, address, or parcel number, then follow the online appeal workflow. This is the fastest method. File at least 2-3 days before the deadline to avoid being locked out by a technical issue or portal slowdown. Screenshot your confirmation page and save your filing ID.
Send your completed PT-311A form (or a letter stating your appeal) to:
Cobb County Board of Tax Assessors P.O. Box 649 Marietta, GA 30061
Cobb County accepts a simple letter as an appeal. The letter must include the property street address, the Parcel ID Number, and a brief explanation of why you believe the assessed value is too high.
Your appeal is deemed filed as of the USPS postmark date, not the date it arrives. Use certified mail or statutory overnight delivery for proof. A metered mail stamp from your office postage machine may not be accepted as a valid postmark. Use the post office counter.
For a walkthrough of the PT-311A form, see our PT-311A Georgia appeal guide.
File at 736 Whitlock Avenue, Suite 200, Marietta, GA 30064. Office hours are Monday through Friday, 8:00 AM to 5:00 PM. Bring a copy of your completed form (or letter) and ask the clerk to stamp a second copy as your receipt.
Cobb County does not have permanent satellite offices for the Board of Tax Assessors. The Whitlock Avenue office is the only in-person filing location.
If you have questions, call (770) 528-3100.
The strongest evidence in a property tax appeal is comparable sales data: recent sales of similar homes that demonstrate your property's actual market value.
Focus on finding 3-5 properties that sold in 2025 (for a 2026 appeal) within your neighborhood or subdivision, with square footage within 10-15% of your home's living area. Present them in a price-per-square-foot analysis. If your comps show an average of $180 per square foot and the county assessed your home at $210 per square foot, you have a clear, data-driven argument.
Check your county assessor's property card for data errors as well. Incorrect square footage, wrong lot size, or an inaccurate condition rating can inflate your assessed value. Correcting these errors can be just as effective as presenting comparable sales.
For a deeper look at building your evidence package, see our guides on how to find comparable properties and property tax appeal evidence that wins. For the full Cobb County appeal process, read our Cobb County property tax appeal guide.
In Georgia, a BOE hearing can technically result in a value higher than the county's original assessment. However, this outcome is rare. The board's role is to determine fair market value based on evidence, and most panels will not increase a value unless the county appraiser presents compelling evidence that the property was underassessed. You should not let this possibility discourage you from filing, but you should only appeal when you have solid comparable sales evidence supporting a lower value.
For most residential property tax appeals in Georgia, you do not need a lawyer. The Board of Equalization process is designed for homeowners to represent themselves. If you have 3-5 strong comparable sales and can present your case clearly in 7-10 minutes, you are well-equipped to handle a BOE hearing on your own.
Consider professional help if: your property is valued above $500,000 and you are considering a hearing officer, you plan to pursue arbitration (which requires a certified appraisal), or your case reaches Superior Court. For a straightforward residential appeal based on comparable sales, DIY is the standard approach, and statewide data shows that homeowners who show up with evidence win the majority of the time.
If you miss the 45-day appeal deadline, you cannot appeal your property tax assessment for the current tax year. There are no extensions, hardship exceptions, or late-filing provisions in Georgia law. You must wait until next year's assessment notice arrives and file within the new 45-day window.
To avoid this situation: check your county assessor's website for your notice as soon as assessment season begins (typically April through June depending on your county), sign up for electronic notice delivery if your county offers it, and set a calendar reminder the day your notice is posted. Do not rely on mail delivery. Postal delays have caused homeowners to miss deadlines in past years.