Real Estate Tax Calc
How the half-year convention works
The MACRS half-year convention is a simplifying assumption built into the depreciation system. Rather than calculating depreciation based on the exact date you placed an asset in service — which would require knowing whether you bought the printer on January 2 or November 29 — Congress chose to treat all personal property additions as if they arrived at the midpoint of the tax year. For a calendar-year taxpayer, that midpoint is July 1.
The practical effect is straightforward: in year one, every piece of personal property you place in service receives exactly half of what would be a full-year deduction. A 5-year asset placed in service on January 1 gets the same first-year deduction (before bonus) as a 5-year asset placed in service on December 31. Both are treated as having entered service on July 1.
The same logic applies to dispositions. When you sell or retire an asset mid-life, the half-year convention treats it as disposed of on July 1 of the disposition year — so you get a half-year of depreciation in the final year regardless of whether you sold it in February or October.
Year-one and final-year deductions under the half-year convention
For a 5-year asset with a cost of $10,000 depreciated using the 200% declining-balance method (the MACRS default for 5-year property), the depreciation percentages from IRS Table A-1 in Publication 946 reflect the half-year convention automatically. The year-one percentage is 20% (half of the 40% full-year rate), and the final year (year 6) is the remaining half-year pickup. The convention is already baked into the IRS percentage tables — you don't have to calculate it separately if you use the tables.
For straight-line depreciation over 15 years (such as QIP), the half-year convention produces a year-one deduction of 1/30 of the basis (half of 1/15), and a year-16 pickup of another 1/30, with years 2–15 each receiving 1/15 of the basis.
Why it matters for declining-balance MACRS
The half-year convention interacts meaningfully with the declining-balance method used for 5-year and 7-year MACRS property. The 200% declining-balance method front-loads deductions by applying double the straight-line rate to the declining book value. The half-year convention in year one essentially cuts the first-year declining-balance rate in half.
For example, a 7-year MACRS asset uses the 200% declining-balance method, which starts with a rate of 2/7 ≈ 28.57% per year. With the half-year convention, year one is 28.57% × 0.5 = 14.29% of cost. Year two applies the same 28.57% rate but to the remaining balance after year one's deduction. By year 5, MACRS typically switches to straight-line because the straight-line rate on the remaining balance exceeds the declining-balance rate — the switch-over maximizes the deduction in later years.
The IRS publishes pre-computed percentage tables in Publication 946, Appendix A, that incorporate the half-year convention for every MACRS class and method. Using those tables is simpler than calculating the declining-balance manually each year, but understanding the underlying mechanics helps when you need to work with partial-year assets, short tax years, or assets acquired mid-depreciation schedule.
The mid-quarter convention trigger
The half-year convention is the default for personal property. But Congress recognized that the half-year rule could be gamed: a taxpayer who buys $1 million of equipment on December 29 receives six months of depreciation under the half-year convention, even though the asset was owned for only three days. To prevent bunching of late-year additions, the mid-quarter convention kicks in automatically if more than 40% of the total depreciable basis of all personal property placed in service during the year is placed in service in the last three months (Q4).
The mid-quarter convention is an all-or-nothing rule: if it triggers, it applies to every piece of personal property placed in service that year — not just the Q4 assets. Under the mid-quarter convention, each asset is treated as placed in service at the midpoint of the quarter in which it actually entered service:
- Q1 mid-point: February 15 → 10.5 months in year one (87.5% of a year)
- Q2 mid-point: May 15 → 7.5 months in year one (62.5% of a year)
- Q3 mid-point: August 15 → 4.5 months in year one (37.5% of a year)
- Q4 mid-point: November 15 → 1.5 months in year one (12.5% of a year)
For Q1 and Q2 assets, the mid-quarter convention is more favorable than the half-year convention (they get more than half a year of depreciation). For Q4 assets, it is significantly less favorable. If the mid-quarter convention triggers because of large Q4 purchases, Q1 and Q2 assets that would have received 50% of a full year under the half-year rule instead receive 87.5% or 62.5% — a pleasant surprise. But Q4 assets drop to 12.5%, which can substantially reduce the year's total deduction if those assets dominate.
The mid-month convention for real property
Buildings and building improvements that are classified as real property use a different convention — the mid-month convention under IRC §168(d)(2). Under this rule, the property is treated as placed in service in the middle of the month in which it actually enters service. For a rental property first available to rent in August, the mid-month convention gives 4.5 months (August 15 through December 31) of depreciation in year one — approximately 4.5/12 = 37.5% of a full year's deduction.
The mid-month convention applies to:
- 27.5-year MACRS residential rental property
- 39-year MACRS nonresidential commercial property
- 30-year ADS residential rental property
- 40-year ADS nonresidential real property
- QIP (15-year) — wait, does it? No: QIP is 15-year personal property for convention purposes even though it is a structural improvement. QIP uses the half-year convention (or mid-quarter), not the mid-month convention. This surprises many practitioners.
The distinction matters: QIP placed in service in December receives half a year of depreciation under the half-year convention (or 1.5 months under mid-quarter if triggered), while a new building placed in service in December receives only about 0.5 months under the mid-month convention. For year-one deductions, the half-year rule is more generous for QIP than the mid-month rule would be.
Worked example: half-year convention in practice
An investor places $120,000 of 5-year MACRS personal property (appliances, carpeting, and fixtures identified in a cost segregation study) in service in March 2025. No other personal property is placed in service during 2025. The investor uses the 200% declining-balance method (the MACRS default for 5-year property).
Full-year rate (200% DB on 5-year): 2 ÷ 5 = 40%
Year-1 with half-year convention: $120,000 × 40% × 0.5 = $24,000
Year-2: remaining basis = $120,000 − $24,000 = $96,000; apply 40% DB = $96,000 × 40% = $38,400
Year-3: remaining = $57,600; 40% DB = $23,040
Year-4: remaining = $34,560; MACRS switches to straight-line here because SL on remaining life (2.5 years) is larger: $34,560 ÷ 2.5 = $13,824 > $34,560 × 40% = $13,824. Tie goes to SL.
Year-5: $20,736
Year-6 (final half-year): $10,368
Total: $24,000 + $38,400 + $23,040 + $13,824 + $20,736 + $10,368 = $130,368 ≠ $120,000.
Note: Using the precise MACRS table percentages (Publication 946, Table A-1) resolves rounding and produces exactly $120,000 total. The above is illustrative — always use the IRS percentage tables for actual computations.
Impact on bonus depreciation
When bonus depreciation applies to personal property, the convention affects only the regular MACRS deduction on the remaining basis, not the bonus itself. Bonus depreciation is computed on the full unadjusted depreciable basis before any convention:
Example: 7-year MACRS asset, $50,000 cost, 60% bonus (2024 rate):
- Bonus deduction: $50,000 × 60% = $30,000
- Remaining basis: $50,000 × 40% = $20,000
- Year-1 regular MACRS on $20,000 (half-year, 200% DB): $20,000 × (2/7) × 0.5 = $2,857
- Total year-1 deduction: $30,000 + $2,857 = $32,857
If 100% bonus applies, the entire $50,000 is deducted in year one. There is no remaining basis, so the half-year convention has no effect — there is nothing left to depreciate in later years.
After a partial bonus (not 100%), the regular MACRS schedule on the remaining basis runs for the full recovery period — 7 years for 7-year property — with the same half-year (or mid-quarter) convention governing year one of the regular schedule.
How to report conventions on Form 4562
Form 4562, Depreciation and Amortization, requires you to state the MACRS method and convention for each asset (or group of assets with the same class, method, and convention):
- Part III, Section A (lines 19a–19i): MACRS Deductions for Assets Placed in Service. For each row, you enter the classification (5-yr, 7-yr, etc.), the month/year placed in service, the basis, the recovery period, the method (200 DB, 150 DB, or SL), and the convention (HY for half-year, MQ for mid-quarter, MM for mid-month).
- Part III, Special Depreciation Allowance (line 14): Bonus depreciation is reported here before regular MACRS.
When the mid-quarter convention applies, use "MQ" as the convention code and apply the correct percentage table (Publication 946 Table A-5, A-6, A-7, or A-8 depending on the recovery period and quarter placed in service). The IRS computer systems match your reported convention against the percentage used, so consistency between the form and the table is important.
For real property placed in service during the year, the form asks for the month placed in service (1–12), and you use the mid-month convention table (Table A-7 or A-7a in Publication 946).
Short tax years and the half-year convention
In the year a business is formed or liquidated — resulting in a short tax year of fewer than 12 months — the half-year convention rules change. For a short tax year, the first year of depreciation is computed differently: the asset is treated as placed in service on the first day of the second half of the short tax year. For example, if the tax year runs only from April 1 to December 31 (nine months), the midpoint is September 1. Property placed in service any time during that short year is treated as placed in service September 1, giving roughly four months of depreciation. The IRS guidance in Publication 946 provides detailed rules for short-year calculations.
Frequently asked questions
What is the MACRS half-year convention?
Under IRC §168(d)(1), all personal property (5-year, 7-year, 15-year MACRS) placed in service during the tax year is treated as placed in service at the midpoint of the year — July 1 for a calendar-year taxpayer. This means year one and the final year of depreciation each cover only half a year, regardless of the actual placement date.
When does the mid-quarter convention replace the half-year convention?
When more than 40% of the aggregate depreciable basis of all personal property placed in service during the tax year is placed in service in the last three months (Q4), the mid-quarter convention applies to all personal property placed in service that year — even assets acquired earlier in the year.
Does the half-year convention apply to residential or commercial buildings?
No. Real property (27.5-year residential rental and 39-year commercial) uses the mid-month convention, not the half-year convention. Under the mid-month rule, the property is treated as placed in service in the middle of the month it actually enters service.
How does the half-year convention interact with bonus depreciation?
Bonus depreciation applies to the full unadjusted depreciable basis first, before any half-year convention calculation. The convention only affects the regular MACRS deduction on the remaining basis after bonus. If 100% bonus depreciation applies, there is no remaining basis and no convention to apply.
Educational information and estimates only. Not tax advice. Tax rules change and vary by situation; consult a qualified tax professional before acting.