The timber depletion deduction lets you recover the capital tied up in your standing trees as you harvest or sell them, offsetting a share of your original investment against each sale. You calculate it by dividing the adjusted basis in a timber account by the merchantable volume currently in that account to get a per-unit rate, then multiplying the rate by the units cut or sold during the tax year. The mechanics rest on three things done in order: establishing basis, organizing the timber into accounts, and updating volume before every calculation.
Establishing Your Timber Basis
Basis is the dollar figure that anchors every depletion calculation you will ever make on the property. Getting it right at the outset matters more than almost anything else in timber taxation, and how you acquired the land dictates where basis starts.
If you bought the property, your basis is what you paid.1Office of the Law Revision Counsel. 26 USC 1012 – Basis of Property Cost If you inherited it, basis resets to the fair market value on the date the previous owner died, which often produces a significantly higher figure than the decedent originally paid.2Office of the Law Revision Counsel. 26 USC 1014 – Basis of Property Acquired From a Decedent If the estate executor elected an alternate valuation date under Section 2032, basis uses that date instead. Timber received as a gift generally carries over the donor’s basis, adjusted for any gift tax paid; if fair market value at the time of the gift was lower than the donor’s basis, you use the lower value when calculating a loss on a later sale.3Office of the Law Revision Counsel. 26 USC 1015 – Basis of Property Acquired by Gifts and Transfers in Trust
Separating Land From Timber
Your acquisition cost covers both the land and the standing trees, but only the timber portion qualifies for depletion. Land is permanent and not consumed by harvesting, so its value must be carved out and tracked in a separate account.4eCFR. 26 CFR 1.611-3 – Rules Applicable to Timber Most landowners hire a consulting forester to estimate the fair market value of the standing timber versus the bare land at the time of acquisition. That allocation becomes the foundation for every depletion deduction you claim, so the appraisal documentation should be kept as a permanent record.
Capitalized Acquisition Costs
Purchase price alone does not capture your full basis. Expenses tied directly to acquiring the property get added in: timber cruises and appraisals done in connection with the purchase, boundary surveys, title opinions, legal fees, and broker commissions. All of these costs get allocated between the land and timber accounts proportionally, in the same way the purchase price itself is split.5USDA Forest Service. Tax Tips for Forest Landowners 2025 Tax Year
Setting Up Timber Accounts
Federal regulations require you to organize your timber into depletion accounts called blocks. Each block groups timber that would logically be managed, harvested, or sent to the same destination together. Blocks can be defined by geographic boundaries, logging units, management areas, or the mill where the logs will be processed.4eCFR. 26 CFR 1.611-3 – Rules Applicable to Timber
Within a block, you can further separate timber into accounts based on species or product class. A landowner with both high-value sawtimber and lower-grade pulpwood on the same tract would typically create separate accounts for each if they carry different per-unit values. Timber acquired under a cutting contract must always be tracked in a separate account and cannot be lumped into an existing block.
Every account records both the volume of timber and its allocated basis. Volume is measured in the standard unit for the product: thousands of board feet for sawlogs, cords or tons for pulpwood.4eCFR. 26 CFR 1.611-3 – Rules Applicable to Timber Pairing physical inventory with financial basis is what makes the depletion calculation work. Without accurate volume records, the IRS has no way to verify your per-unit deduction, and neither do you.
Calculating the Depletion Unit
The depletion unit is the dollar value you assign to each board foot, ton, or cord in a timber account. Divide the adjusted basis for the account by the total merchantable volume currently in that account. If your sawtimber account has a basis of $50,000 and holds 500,000 board feet, the depletion unit is $0.10 per board foot.
The critical word in that formula is “currently.” Forests grow. Trees that were too small to count as merchantable five years ago may have crossed that threshold. Others may have been lost to disease or storms. Before calculating your depletion unit for any sale, update the volume figure in the denominator to reflect growth additions and losses since the last adjustment.6Office of the Law Revision Counsel. 26 USC 611 – Allowance of Deduction for Depletion If operations or development reveal that recoverable volume is greater or less than previously estimated, the statute requires you to revise the estimate and base future depletion on the new figure.
The easiest way to get an updated volume is to have the forester managing your sale cruise the entire stand, not just the trees marked for harvest. That produces fresh data for both the numerator (trees being sold) and the denominator (total standing volume) at the same time. Skipping this step is where many timber owners create problems. An outdated volume figure either inflates or understates the depletion unit, and either direction can trigger trouble on audit.
Applying the Deduction to a Sale
Once you have a current depletion unit, the deduction is straightforward multiplication. Take the units actually harvested and sold during the tax year and multiply by the depletion unit for that account.
Say your sawtimber account carries a depletion unit of $10 per ton and you sell 500 tons. The depletion deduction is $5,000. If you also sell 3,000 tons of pulpwood from a separate account with a depletion unit of $1 per ton, that deduction is $3,000. The total basis recovered across both accounts is $8,000.5USDA Forest Service. Tax Tips for Forest Landowners 2025 Tax Year
The calculation runs separately for each account where harvesting occurred during the year. As you harvest and deduct, the adjusted basis in each account declines. Once the entire basis has been recovered, any further harvest income from that account is fully taxable with no depletion offset.
One boundary worth flagging: timber uses cost depletion only. Unlike oil, gas, and mineral properties, timber is not eligible for percentage depletion. Your deduction is always limited to your actual investment, calculated on a per-unit basis.
Reporting the Deduction
When you claim a depletion deduction, sell timber, or exchange timber in a qualifying transaction, you generally file Form T (Timber), the Forest Activities Schedule, with your return. Form T is where your basis calculations, account structure, and harvest volumes get laid out. Gains and losses on standing timber are reported on Form 4797.7Internal Revenue Service. Instructions for Form T (Timber)
Small Owner Exemption
You are not required to file Form T if you only make occasional timber sales, defined as one or two sales every three or four years. You must still keep adequate records of those transactions and other timber-related activities during the year.7Internal Revenue Service. Instructions for Form T (Timber) The exemption spares the paperwork, not the recordkeeping.
Records and Penalties
Timber records carry an unusually long retention requirement. Regulations require you to keep maps, acquisition records, timber cruise data, and harvest documentation for as long as their contents may be relevant to any federal tax matter.8Internal Revenue Service. Timber Casualty Loss Audit Techniques Guide In practice, that means holding original purchase contracts, appraisals, cruise reports, and boundary surveys as permanent records. The basis documents remain material until the last tree from that acquisition is sold or the property changes hands.
If the IRS determines that an understatement resulting from a bad depletion calculation was due to negligence or a substantial understatement of income, the accuracy-related penalty is 20% of the resulting tax underpayment.9Internal Revenue Service. Accuracy-Related Penalty Unsupported volume estimates are the most common trigger in timber audits. A professional cruise documenting both total inventory and harvest volume is the most reliable defense.