AMT Tax Preference Items

The Alternative Minimum Tax (AMT) recalculates income tax liability after adding back certain deductions and income items that the regular tax system allows. These preference items are the specific adjustments—such as depreciation, intangible asset amortisation, and certain interest deductions—that make the AMT base larger and therefore increase the likelihood that a high-income taxpayer will owe AMT rather than regular tax.

What are preference items and why they exist

The AMT operates on a different tax base than the regular income tax system. Where regular tax allows certain deductions without limit, the AMT either disallows them or shrinks them. The difference between what regular tax allows and what AMT allows is called a preference item or adjustment.

The philosophy behind preference items is simple: the regular tax system contains deductions and exclusions designed to encourage certain behaviours (investment, charitable giving, home ownership). These incentives are valuable, but they can allow high-income individuals to reduce their tax bills below what Congress deemed a fair minimum share. Preference items clawback some of these benefits on a parallel tax return—the AMT—to ensure that wealthy taxpayers contribute a baseline amount.

Preference items come in two flavours: deductions the AMT disallows or limits, and income adjustments that the AMT includes. Both expand the tentative minimum tax base.

Major categories of preference items

Depreciation and amortisation: This is historically the largest single preference item for businesses and real estate investors. Under regular tax, businesses can use accelerated depreciation methods (such as double-declining-balance or MACRS) to deduct large amounts early in an asset’s life. The AMT requires use of a slower straight-line method. The difference in deductions between the two methods is added back.

For example, a firm purchasing machinery might deduct $100,000 in year one under regular tax but only $50,000 under AMT straight-line. The $50,000 difference is a preference item that increases the AMT base.

Intangible asset amortisation: When a business acquires intangible-assets (patents, copyrights, licences, contracts), regular tax allows amortization over the asset’s useful life, often determined by the acquiring company. The AMT requires a specific 40-year amortisation period for most intangibles. The faster deduction under regular tax is clawed back.

Passive activity losses: Real estate partnerships and S-corporation losses from passive activities are treated differently under AMT. Regular tax allows certain passive losses to offset active income for high-income taxpayers in specific years. The AMT is stricter, disallowing or deferring more of these losses. The timing difference expands the current year’s AMT base.

Incentive stock option (ISO) spread: When an executive exercises an ISO below fair market value, the spread (difference between exercise price and market value) is not deducted for regular income tax purposes. However, it is included in the AMT base as a preference item. This can trigger substantial AMT liability in the year of exercise, even though no regular income tax is due.

Tax-exempt bond interest: Interest earned on private-activity bonds (a specific class of municipal bonds used for non-public purposes) is excluded from regular taxable income but included in the AMT base.

Disallowed deductions: Certain deductions allowed under regular tax—such as mining exploration costs, pollution control facility amortisation, and certain farm losses—are not allowed under AMT. The amount of the regular deduction becomes a preference item.

How preference items interact with the AMT exemption

The AMT exemption starts at a high threshold (in the range of $100,000–$150,000 for individuals, depending on filing status and year). But as a taxpayer’s preference items grow, they eventually exceed the exemption. Once the exemption is fully phased out by income, all preference items add directly to the tax base, with no relief.

A taxpayer with $50,000 in preference items and a full AMT exemption might owe little or no AMT. But a taxpayer with $200,000 in preference items and a phased-out exemption could face severe AMT liability.

Timing and deferral effects

Many preference items create timing differences rather than permanent exclusions. For example, the difference between accelerated and straight-line depreciation reverses in later years. A firm claiming $50,000 extra depreciation in year one has a $50,000 preference item but will have negative preference items (i.e., lower AMT deductions than regular deductions) in future years as the accelerated deduction catches up.

Similarly, passive losses disallowed in one year may be allowed in later years once passive income is earned. The AMT can create a deferral trap: high preference items in year one trigger AMT; lower items in later years mean the AMT liability cannot be recovered through credits.

Form 6251 and calculating preference items

Taxpayers subject to AMT complete Form 6251 (Alternative Minimum Tax—Individuals), which lists each preference item separately. Preferential items are added back line-by-line: depreciation adjustment, amortisation adjustment, passive loss adjustment, and so on. The sum of all preference items, combined with the tax base from regular tax, determines the tentative minimum tax.

For businesses and partnerships, preference items flow through to owners via Schedule K-1 from partnerships or S-corporations, requiring owners to account for their share of preference items on their individual Forms 6251.

Strategic implications

High-income earners and business owners must monitor preference items carefully. In years when depreciation or amortisation creates large add-backs, the risk of AMT liability rises. Some taxpayers manage preference item exposure by:

• Timing asset purchases to spread depreciation across multiple years
• Electing to use straight-line depreciation for both regular and AMT purposes (removing the preference item)
• Structuring real estate or partnership investments to minimise passive loss disallowances

Others use cost-of-debt and interest deduction strategies to reduce overall income, offsetting the expansion of the base from preference items.

See also