What does MACRS stand for?

Modified Accelerated Cost Recovery System. Codified at IRC §168, MACRS is the depreciation method required for most tangible property placed in service after December 31, 1986. It replaced the prior ACRS system under the Tax Reform Act of 1986.

Which property uses 27.5 years vs 39 years?

Residential rental property (defined as a building with 80% or more of its gross rental income from dwelling units, per IRC §168(e)(2)(A)) depreciates over 27.5 years. Nonresidential real property depreciates over 39 years. Property that fails the 80% residential test follows the 39-year schedule even if some portion is residential.

When does ADS (alternative depreciation system) apply?

ADS applies in three situations: (1) elected voluntarily by the taxpayer, (2) required for tax-exempt use property, listed property used 50% or less for business, property used predominantly outside the U.S., and farming property under IRC §168(g), or (3) required when a real property trade or business elects out of §163(j) interest limitations.

What is the half-year convention?

The half-year convention treats all property placed in service during the year as placed in service at the midpoint of the year. Half a year of depreciation is allowed in both the first year and the year of disposition. It applies to most personal property (5-year, 7-year MACRS) unless the mid-quarter convention is required.

What is the mid-quarter convention?

The mid-quarter convention applies when more than 40% of total depreciable basis (excluding real property and listed property) is placed in service in the last quarter of the tax year. Each asset is treated as placed in service at the midpoint of its quarter — yielding 87.5% (Q1), 62.5% (Q2), 37.5% (Q3), or 12.5% (Q4) of a full year's depreciation in year 1.

Can I change my MACRS classification after the property is in service?

Yes — a misclassification is a method change. File Form 3115 under Rev. Proc. 2015-13 with automatic consent. The §481(a) adjustment captures the cumulative effect of the corrected method in the year of change, without amending prior returns. This is the standard mechanism for cost segregation studies on previously-acquired property.

MACRS — IRS Depreciation Rules

Plain-English definition

MACRS — the Modified Accelerated Cost Recovery System — is the depreciation method required under IRC §168 for most tangible property placed in service after December 31, 1986. It assigns a class life and recovery period to each asset, applies one of three averaging conventions (half-year, mid-quarter, or mid-month), and uses either the declining-balance method (for shorter-lived property) or the straight-line method (for real property).

MACRS is the default. The General Depreciation System (GDS) applies unless the Alternative Depreciation System (ADS) is required or elected.

What the law says

The statute reads, in part:

26 U.S.C. § 168(a)

“Except as otherwise provided in this section, the depreciation deduction provided by section 167(a) for any tangible property shall be determined by using— (1) the applicable depreciation method, (2) the applicable recovery period, and (3) the applicable convention.”

Source: Cornell LII · IRS.gov

The three “applicable” determinations — method, recovery period, and convention — are the entire framework. Every classification question under MACRS reduces to picking among these three.

Class lives and recovery periods

Class life is assigned by Rev. Proc. 87-56, which lists ~150 asset classes covering essentially every business property type. Recovery period is then a function of class life:

Class life (Rev. Proc. 87-56)	GDS recovery period	Typical examples
4 years or less	3 years	Race horses over 2, taxis
5–10 years	5 years	Automobiles, computers, light trucks, dairy cattle, qualified film/TV
10–16 years	7 years	Office furniture, fixtures, agricultural machinery
16–20 years	10 years	Vessels, single-purpose agricultural structures
20–25 years	15 years	Land improvements (parking lots, sidewalks, landscaping), restaurant property, QIP
25+ years (real property)	27.5 yrs	Residential rental property
25+ years (real property)	39 yrs	Nonresidential real property (commercial buildings)

The full classification table (147 entries from Rev. Proc. 87-56) is available at /class-lives/table/.

GDS vs ADS

	GDS (General)	ADS (Alternative)
Method	Declining-balance, switching to straight-line	Straight-line
Recovery periods	3, 5, 7, 10, 15, 20, 27.5, 39 years	Longer than GDS for most classes; 30 yrs residential, 40 yrs nonresidential
When required	Default — applies unless ADS is required	(a) Tax-exempt use property; (b) listed property used ≤50% for business; (c) property used outside U.S.; (d) farming property (§168(g)(7)); (e) §163(j) election
When elected	(Cannot elect into GDS — it’s the default)	Optional for any depreciable property — irrevocable election made annually

Real-property trade or business election under §163(j): A taxpayer that elects out of the business-interest limitation under §163(j)(7) must use ADS for nonresidential real property (40 yrs), residential rental property (30 yrs), and QIP (20 yrs). This election is irrevocable and forecloses 100% bonus depreciation on the affected classes for the life of the property.

Conventions

The convention determines how much depreciation is taken in the first and last partial years.

Half-year convention. Most personal property (5-year, 7-year). All property placed in service during the year is treated as placed in service at the midpoint of the year — half a year of depreciation in year 1, half a year in the disposition year.

Mid-quarter convention. If more than 40% of total depreciable basis (excluding real property and listed property) is placed in service in Q4, each asset is treated as placed in service at the midpoint of its actual quarter:

Q1: 87.5% of full-year depreciation
Q2: 62.5%
Q3: 37.5%
Q4: 12.5%

The mid-quarter test is calculated annually and on a property-class basis — it’s possible to be in the half-year convention for 5-year property and the mid-quarter convention for 7-year property in the same year, depending on placement timing.

Mid-month convention. Required for all real property (27.5-yr and 39-yr classes). Each property is treated as placed in service at the midpoint of the calendar month — yielding 11.5 months of depreciation in year 1 if placed in service on January 1, 0.5 months if placed in service on December 31.

Bonus depreciation interaction

IRC §168(k) bonus depreciation is layered on top of MACRS — not in lieu of it. The mechanics:

Determine the property’s MACRS class life and recovery period under §168.
If the recovery period is 20 years or less and the property otherwise qualifies, take §168(k) bonus depreciation on the full basis in year 1 (currently 100% for property placed in service after January 19, 2025, per OBBBA).
The remaining basis (after bonus, typically $0 at 100%) depreciates over the MACRS recovery period using the applicable method and convention.

Bonus depreciation does not apply to 27.5-year residential rental or 39-year nonresidential real property — those classes exceed the 20-year cap. But the 15-year and shorter components identified through cost segregation on those buildings do qualify.

§179 interaction

IRC §179 immediate expensing operates separately from MACRS. The taxpayer elects §179 expensing on qualifying property up to the annual dollar limit ($1.29M for 2026, phased out above $3.22M of investment). The §179 deduction is taken first, then bonus depreciation, then MACRS on the residual basis.

Where the same property qualifies for both §179 and 100% bonus, the choice is largely about taxable-income limitations: §179 cannot create a net loss (excess carries forward), while bonus depreciation can.

Recapture interaction

When MACRS property is disposed of, depreciation recapture applies under IRC §§1245 or 1250. The split:

Personal property (5-year, 7-year classes, and the components reclassified into them through cost segregation): §1245 recapture at ordinary income rates on the full depreciation taken.
Real property (27.5-year, 39-year classes): §1250 recapture, with the bulk of the depreciation taxed as “unrecaptured §1250 gain” at a 25% maximum rate.

The §1245 vs §1250 distinction is the core reason cost segregation is consequential at sale — components classified into accelerated buckets generate ordinary-income recapture rather than capital-gain treatment.

Common errors

Five recurring misclassifications, each cited in the IRS Cost Segregation Audit Techniques Guide:

Treating tenant-improvement allowances as the landlord’s basis. If the landlord pays cash to the tenant for improvements the tenant constructs and owns, the landlord has no depreciable basis. The tenant captures the depreciation.
Misclassifying decorative finishes as 39-year structural. Decorative wall coverings, accent lighting, and removable interior partitions qualify as 5-year personal property under Treas. Reg. §1.48-1(c) when they pass the permanence test. The IRS ATG Chapter 3 enumerates the test.
Land improvements treated as part of the 39-year building. Parking lots, sidewalks, site lighting, monument signage, fencing, and landscaping are 15-year land improvements under Rev. Proc. 87-56 Class 00.3 — not part of the building’s 39-year basis.
Section 1245 vs §1250 recapture confusion on sale. Selling property after a cost segregation study without correctly bifurcating §1245 recapture (on the 5/7/15-year reclassified components) from §1250 recapture (on the remaining building basis) is the single most common cost-seg disposition error.
Failing to file Form 3115 for missed depreciation. When a cost segregation study identifies depreciation that should have been claimed in prior years, Form 3115 under Rev. Proc. 2015-13 captures the §481(a) adjustment in the year of change. Amending three prior returns is not the alternative — it’s the wrong mechanism.

Sources

Statute: 26 U.S.C. § 168 — Cornell LII · IRS Pub. 946
Regulations: Treas. Reg. § 1.168-1 through § 1.168-6 (and § 1.48-1(c) for the permanence test on personal property classification)
Revenue procedures: Rev. Proc. 87-56 (asset class table); Rev. Proc. 2015-13 (Form 3115 procedures); Rev. Proc. 2026-08 (current automatic-consent procedures for §168(k) late elections)
IRS publications: Pub. 946 — How to Depreciate Property; Pub. 5653 — Cost Segregation Audit Techniques Guide; Pub. 527 — Residential Rental Property
Cases: Hospital Corporation of America v. Commissioner, 109 T.C. 21 (1997) — the seminal cost segregation case interpreting MACRS personal/real property classification

Working through a cost segregation study under MACRS? The engineering classification of building components into the 5-, 7-, and 15-year MACRS buckets is the actual mechanism cost segregation operates on. A working example of how each MACRS class maps to component-level reclassification on a commercial property shows the process end-to-end.

MACRS — Modified Accelerated Cost Recovery System