What Is Excess IDC and How Does It Affect Your AMT?

Excess intangible drilling costs are a tax preference item that can drag you into the Alternative Minimum Tax and claw back part of the upfront deduction that made an oil and gas investment attractive. The relationship between excess IDC and AMT works in layers: the excess amount is the gap between the IDC you actually deducted and what a 120-month amortization would have given you, then that gap is reduced by 65% of your net oil and gas income, and independent producers get a further exception that often zeroes the preference out entirely.¹ For 2026, AMT exemptions of $90,100 for single filers and $140,200 for joint filers absorb some of what remains, but investors with large IDC deductions relative to their oil and gas income can still owe AMT.²

What Counts as IDC in the First Place

IDC covers the non-salvageable costs of drilling and preparing a well: labor, fuel, repairs, hauling, supplies, mud, chemicals, ground clearing, road building, surveying, geological work, and temporary structures needed for drilling.³ The common thread is that these expenditures have no salvage value once drilling ends. Under Section 263(c), an operator holding a working interest can elect to deduct these costs immediately instead of capitalizing them.⁴ That immediate write-off is the whole appeal, and it is also what sets up the AMT problem.

How the Excess Amount Is Calculated

Section 57(a)(2) builds the preference in two stages.

Stage one is the excess amount itself. Take the IDC you actually expensed on productive wells (dry holes are excluded from this calculation). Subtract what you would have deducted if those same costs had been capitalized and amortized in a straight line over 120 months starting when the well began producing. The difference is your excess IDC for the year.¹

Stage two is the 65% net income offset. You do not report the full excess. You report only the portion that exceeds 65% of your net income from all oil, gas, and geothermal properties for the year. Net income here means gross income from those properties minus allocable deductions, but with the excess IDC itself excluded from the deduction side.¹ When refiguring that net income for AMT purposes, use only income and deductions allowed under the AMT rules, not your regular tax figures.⁵

A quick example. You expensed $1,000,000 in IDC on productive wells this year. The 120-month amortization would have given you $100,000 in the same year. Your excess IDC is $900,000. Your net oil and gas income is $1,200,000, so the 65% offset is $780,000. The reportable preference is $900,000 minus $780,000, or $120,000. In heavy drilling years, when income has not caught up to costs, the offset shelters less, and the reportable preference grows.

The Independent Producer 40% Exception

Independent producers get a significant break the basic formula does not reveal. If you are not an integrated oil company (that is, you are not involved in substantial refining or retailing), the IDC preference does not apply at all unless it exceeds 40% of your alternative minimum taxable income calculated with the preference included.⁵ If the preference stays at or below 40% of AMTI, you report zero on Form 6251 line 2t. Only the amount above 40% of AMTI gets reported.

The practical result is that many independent operators and their investors never owe AMT on excess IDC, especially in years when other income keeps AMTI high relative to the drilling deduction. Run the math before assuming an AMT hit is coming, because the exception can wipe the preference out.

How the Surviving Preference Increases Your AMT

Whatever excess IDC survives the 65% offset and the 40% exception gets added to your regular taxable income along with your other AMT preference items and adjustments to reach your AMTI. From there, subtract the AMT exemption. For 2026 that exemption is $90,100 for single filers and $140,200 for joint filers, and it begins phasing out at $500,000 of AMTI (single) or $1,000,000 (joint).²

AMTI left after the exemption is taxed at 26% on the first $244,500 and 28% on anything above.⁶ You compare that tentative minimum tax to your regular tax and pay whichever is higher. The impact lands hardest in the early years of a drilling program, when IDC deductions are large and production income has not ramped up enough for the 65% offset to absorb the difference.

How to Avoid the AMT Hit: The Section 59(e) Election

If you can see the AMT coming, Section 59(e) lets you amortize some or all of your IDC over 60 months instead of deducting it immediately. Costs amortized under this election are not included in the AMT preference calculation, so this is the most direct way to eliminate or shrink the excess IDC preference.⁷

The election does not have to be all or nothing. You can apply it to any specific dollar amount of IDC you choose.⁷ That means you can expense enough IDC to use up your regular tax deductions without tipping into AMT, then amortize only the slice that would otherwise create an excess preference. The election is made on the timely filed return for the year the costs were paid or incurred, and once made it is effectively irrevocable; the IRS will grant revocation only in rare and unusual circumstances.

The trade-off is straightforward. You give up a large deduction this year in exchange for five years of smaller deductions (roughly 20% per year) and avoid the AMT rate on the excess. For a taxpayer already deep in AMT territory, that trade usually saves money. For someone comfortably below the AMT threshold, taking the full immediate deduction is still the better move. The election is a year-by-year decision, so your choice in 2026 does not bind you in 2027.

Getting the Money Back: The Minimum Tax Credit

AMT paid because of excess IDC is generally not gone forever. Section 53 provides a minimum tax credit that carries forward indefinitely, equal to prior-year AMT that has not yet been used, and it offsets your regular tax liability in any future year where your regular tax exceeds your tentative minimum tax.⁸

The credit calculation excludes AMT attributable to certain exclusion preferences listed in Section 57(a) paragraphs (1), (5), and (7). Excess IDC lives in paragraph (2), which is not on the exclusion list, so IDC-driven AMT fully qualifies for the credit.⁸ In practice, excess IDC produces a timing cost more than a permanent one. You pay AMT upfront, and in later years when your regular tax exceeds the AMT threshold, the credit returns that money. Investors with stable or growing income outside the oil and gas sector often recoup the credit within a few years.

Situations Where the Preference Does Not Apply

Dry Holes

IDC on a dry hole is explicitly carved out of the excess IDC preference. The statute excludes costs incurred in drilling a nonproductive well from the definition.¹ You get the full immediate deduction under the regular tax system, and no AMT preference attaches. This is one of the rare clean tax benefits in oil and gas.

Foreign Wells

The immediate expensing election under Section 263(c) does not apply to wells located outside the United States. Foreign IDC has to be either added to the property’s adjusted basis for cost depletion or amortized over 10 years, so the excess IDC preference calculation is generally irrelevant for foreign properties. Dry hole costs on foreign wells remain currently deductible.⁹

Integrated Oil Companies

Integrated oil companies do not use the preference item calculation at all. Section 291 reduces their IDC deduction by 30% outright, with the disallowed portion amortized ratably over 60 months starting in the month the costs were paid.¹⁰ This is a flat haircut on the immediate deduction rather than a timing item routed through AMT.

Where and How to Report It

Individual taxpayers report the excess IDC preference on line 2t of Form 6251, Alternative Minimum Tax — Individuals.⁵ Independent producers should run the 40% test before entering a figure, because the exception can eliminate or reduce what actually goes on that line.

Investors who participate through partnerships or S corporations receive their IDC information on Schedule K-1, which separately states total IDC paid or incurred and net income from oil and gas properties.¹¹ That separation is what lets you run the 65% offset on your own return. If the K-1 does not break the figures out clearly, request the underlying numbers before finalizing Form 6251.

Taxpayers making a Section 59(e) election attach a statement to their timely filed return for the year the costs were incurred, specifying the exact dollar amount of IDC being amortized.⁷ The amount cannot be expressed as a formula or percentage. It has to be a specific number. Keep drilling invoices, contracts, and well completion records for the full amortization period, because the IRS can ask for support for the original deduction years after the costs were incurred.

1
Office of the Law Revision Counsel. 26 USC 57 – Items of Tax Preference
2
Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026
3
eCFR. 26 CFR 1.612-4 – Charges to Capital and to Expense in Case of Oil and Gas Wells
4
eCFR. 26 CFR 1.263(c)-1 – Intangible Drilling and Development Costs in the Case of Oil and Gas Wells
5
Internal Revenue Service. Instructions for Form 6251 Alternative Minimum Tax – Individuals
6
Office of the Law Revision Counsel. 26 USC 55 – Alternative Minimum Tax Imposed
7
eCFR. 26 CFR 1.59-1 – Optional 10-Year Writeoff of Certain Tax Preferences
8
Office of the Law Revision Counsel. 26 USC 53 – Credit for Prior Year Minimum Tax Liability
9
Office of the Law Revision Counsel. 26 USC 263 – Capital Expenditures
10
Office of the Law Revision Counsel. 26 USC 291 – Special Rules Relating to Corporate Preference Items
11
Internal Revenue Service. Schedule K-1 (Form 1065) – Partners Share of Income, Deductions, Credits