To find the historical fair market value of a home, fix the exact date you need (usually a date of death or the date a gift was made), then work backward from county assessor records, comparable neighborhood sales that closed within about six months of that date, and, when the number will appear on a tax return or in probate, a retroactive appraisal from a licensed appraiser. The IRS uses this figure to set your tax basis, which then drives any capital gain or loss when the home is sold, so accuracy is worth the effort.1Internal Revenue Service. Publication 561 – Determining the Value of Donated Property2Internal Revenue Service. Topic No. 409, Capital Gains and Losses
Start With the Exact Date and the Property’s Condition Then
Every source you pull has to line up with one specific date. If you inherited the home, that date is the previous owner’s date of death, or the alternate valuation date six months later if the executor elected it on Form 706.3Office of the Law Revision Counsel. 26 USC 2032 – Alternate Valuation If the home was a gift, the date is the day the gift was completed.4Office of the Law Revision Counsel. 26 USC 1015 – Basis of Property Acquired by Gifts and Transfers in Trust For an inherited home, basis is generally stepped up to the value on that date, so the number you land on becomes the starting point for any future gain.5Office of the Law Revision Counsel. 26 USC 1014 – Basis of Property Acquired From a Decedent
You also need to reconstruct what the property looked like then, not now. A finished basement, an addition, a new roof, or years of deferred maintenance all change value. Old photographs, dated maintenance receipts, insurance policies from that period, and building permit records help document condition on the target date. Unpermitted work and disrepair matter too.
Pull the property’s legal description or parcel identification number before you start. Every county assigns a unique parcel number that ties the land and any structures to tax records, deed histories, and assessment data. A prior tax bill, deed, or title insurance policy will show it.
Pull County Assessor and Recorder Records
Your county assessor or property appraiser assigns a taxable value to every parcel each tax year. Many counties publish these rolls online in searchable databases where you can look up a parcel by address or ID number and see what the county said the home was worth in a given year.
Assessed value is not the same as fair market value. Most jurisdictions apply an assessment ratio, so the taxable figure represents only a fraction of what the home would actually sell for. If you can find the ratio that applied in the year you need, work backward: divide the assessed value by the ratio. An assessed value of $200,000 in a jurisdiction that assessed at 80% of market implies a market value around $250,000. Ratios change over time, so call the assessor’s office to confirm the one in effect during your target year.
When online records do not reach back far enough, request the physical property card from the assessor or copies of historical deeds from the recorder’s office. Older records sometimes carry handwritten notes about improvements and valuation changes that predate the electronic system. Fees for certified copies are typically modest, often under $10 per document, but vary by jurisdiction.
Find Comparable Sales From the Same Period
The most reliable self-directed method is to find what similar nearby homes actually sold for around your target date. Look inside roughly a one-mile radius for properties with similar square footage, bedroom and bathroom counts, lot size, age, and construction style. Sales that closed within about six months of your date carry the most weight, because prices can shift meaningfully over even a short window.6Federal Housing Finance Agency. Underutilization of Appraisal Time Adjustments
Free tools do a lot of the work. Zillow, Redfin, and Realtor.com maintain databases of past sales, and some listings include original photos that let you compare condition and finishes. Your county’s website may also offer a public sales search showing recorded prices. For dates further back, online platforms may not go past 10 to 15 years, and you may need to ask a local real estate agent to pull historical Multiple Listing Service data.
Once you have at least three comparable sales, calculate a price-per-square-foot range for that neighborhood during that period. Adjust for real differences: a comparable with a pool or a recently renovated kitchen should be adjusted down against a subject property that lacked those features, and up in the opposite case. This gives you a data-backed estimate that works for internal planning. For anything the IRS or a probate court will see, expect to need more.
Hire a Licensed Appraiser for a Retroactive Appraisal
A retroactive (or retrospective) appraisal is a formal opinion of value as of a past date, prepared by a licensed appraiser following the Uniform Standards of Professional Appraisal Practice. Instead of walking through the home in its current state, the appraiser relies on historical sales data, archived market conditions, and whatever documentation exists about past condition. The appraiser must meet USPAP’s competency requirements at the time the work is done, even though the effective date is in the past.
Situations where a professional retroactive appraisal is worth the cost:
- Estate tax filing. Estates that exceed the $15,000,000 federal filing threshold for 2026 must file Form 706, and the IRS expects supportable valuations for every asset listed.7Internal Revenue Service. Estate Tax
- Gift tax filing. The IRS requires either a qualified appraisal or a detailed description of the valuation method when reporting gifted real estate on Form 709.8Internal Revenue Service. Instructions for Form 709
- Significant value. If the home is valuable enough that an accuracy-related penalty would sting, a certified report gives you a defensible figure.
- Probate. Courts often require a formal appraisal when distributing estate assets among beneficiaries.
Fees for retroactive appraisals typically run $500 to $1,500, depending on complexity and how far back the valuation date sits. Assignments involving decades-old dates take longer because archival data is harder to locate. Most reports come back within one to two weeks. The finished product is a certified report detailing the methodology, comparable sales used, and adjustments made, designed to withstand scrutiny from the IRS or a court.
What the IRS Accepts on the Return
The tax return dictates how much documentation your valuation needs to carry.
Form 706 (Estate Tax Return)
Form 706 is due nine months after the date of death, with an automatic six-month extension available on Form 4768 that pushes the deadline to 15 months.9Internal Revenue Service. Instructions for Form 706 For 2026, a return is required only when the gross estate exceeds $15,000,000.10Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 The value reported for the home has to be supportable, which in practice means a retroactive appraisal for anything close to the threshold.
Form 8971 (Basis Reporting)
When Form 706 is required, the executor must also file Form 8971 to report the estate tax value of inherited property to the IRS and to each beneficiary. It is due 30 days after Form 706 is required to be filed (including extensions), or 30 days after Form 706 is actually filed, whichever is earlier.11Internal Revenue Service. Instructions for Form 8971 and Schedule A Each beneficiary gets a Schedule A with the reported value, and they are generally required to use that number as their basis when they later sell.
Form 709 (Gift Tax Return)
A gift of real estate is reported on Form 709 for the year the gift was made, filed by April 15 of the following year. The return must include either a qualified appraisal or a detailed explanation of the valuation method used, along with the donor’s adjusted basis in the property.8Internal Revenue Service. Instructions for Form 709 Adequate disclosure on Form 709 starts the three-year statute of limitations. Skipping the disclosure or undervaluing the property leaves the IRS free to challenge the valuation indefinitely.
Penalties for Getting the Number Wrong
The IRS charges accuracy-related penalties when property values on estate or gift returns come in too low. A 20% penalty applies to any tax underpayment caused by a valuation that is 65% or less of the correct value.12Office of the Law Revision Counsel. 26 USC 6662 – Imposition of Accuracy-Related Penalty on Underpayments If the reported value is 40% or less of the correct amount, the penalty doubles to 40%. The penalty only applies when the underpayment attributable to the misstatement exceeds $5,000.
A parallel set of penalties targets overstated basis on the income tax side. Overstating basis by 150% or more of the correct figure, or claiming an adjusted basis $5,000,000 or more above the correct amount, triggers the same 20% or 40% structure. Inflating a stepped-up basis to shrink a taxable gain when you sell an inherited home can bring the same result as understating the value on Form 706.
A certified retroactive appraisal is the strongest defense. The IRS is far less likely to challenge a value backed by a licensed appraiser working under recognized standards than a self-built estimate assembled from online listings. The appraisal fee is usually a small fraction of what a penalty would cost if the IRS disagrees with the number.