Real Estate Tax Calc
What the half-year convention means
Under the Modified Accelerated Cost Recovery System (MACRS), assets placed in service at any point during the tax year are treated as if they were placed in service at the midpoint of the year. This means you always get a half-year of depreciation in year one — even if you bought the asset on December 31. Similarly, you get a final half-year of depreciation in the year you dispose of the asset.
The half-year convention applies to most personal property (equipment, appliances, furnishings) and short-life assets used in rental property. It does not apply to real property (buildings), which instead uses the mid-month convention — you get a half-month of depreciation for the month the property is placed in service.
When the mid-quarter convention applies instead
There is an important exception. If you place more than 40% of the total depreciable cost of all personal property into service during the fourth quarter of the tax year, the mid-quarter convention applies to all personal property placed in service that year — not just the fourth-quarter assets.
Under the mid-quarter convention, each asset is treated as placed in service at the midpoint of the quarter in which it actually was placed in service. This can significantly reduce year-one depreciation compared to the half-year convention. For example, an asset placed in service in the fourth quarter gets only 1.5 months of depreciation in year one under the mid-quarter rule, instead of 6 months under the half-year rule.
To avoid the mid-quarter convention, be thoughtful about when you buy rental equipment and personal property. Spreading purchases across the year — not front-loading the fourth quarter — keeps you in the more favorable half-year convention.
Real property and the mid-month convention
Residential and commercial buildings use the mid-month convention, which is separate from the personal property rules above. Under this convention, a building placed in service on any day of a given month is treated as placed in service on the 15th of that month — giving you a half-month of depreciation for the placement month.
This is why the year you purchase a rental matters: a December closing gives you about 0.5 months of depreciation for year one, while a January closing gives you 11.5 months. For large buildings, this difference can be $5,000 or more in the first-year deduction. Combined with the placed-in-service date rules, timing your closing can meaningfully accelerate or defer year-one depreciation.
Why conventions exist at all
A convention is a simplifying assumption baked into MACRS so that neither you nor the IRS has to prove the exact day an asset started earning its keep. Without a convention, every taxpayer would argue for the earliest possible placed-in-service date to grab a few extra weeks of depreciation, and every audit would turn into a calendar dispute. By fixing a single deemed date — the midpoint of the year for most personal property, the midpoint of the month for real property, the midpoint of the quarter when the mid-quarter rule applies — the code makes first-year depreciation a mechanical calculation.
The convention also governs the last year. Just as you get a half-year in year one under the half-year convention, you take a half-year in the year you sell or scrap the asset. So a five-year asset is actually spread across six tax years: half in year one, full years in years two through five, and the remaining half in year six. Forgetting the disposition-year half is a common error that leaves depreciation — and basis reduction — on the table.
A worked half-year example
Suppose you buy $10,000 of appliances and furnishings for a rental — five-year MACRS property — and place them in service in March. Under the half-year convention and the 200% declining-balance method, the first-year rate for five-year property is 20%, so you deduct $2,000 in year one even though the assets were in service for ten months. Buy the identical $10,000 of property in November instead and you still deduct exactly $2,000 — the half-year convention ignores the actual month entirely.
The standard five-year MACRS percentages under the half-year convention are 20%, 32%, 19.2%, 11.52%, 11.52%, and 5.76%, summing to 100% across the six tax years. Note the deliberate front-loading: over half the cost is recovered in the first two years. This is the accelerated part of the Modified Accelerated Cost Recovery System, and it is why segregating short-life property out of the 27.5-year building through a cost segregation study produces such large early deductions.
How the mid-quarter test is actually run
The 40% test is not about how much you spent in the fourth quarter as a share of the purchase price — it is a share of all personal property placed in service during the year, measured by depreciable basis and excluding real property and certain other assets. Add up the basis of every piece of personal property you placed in service during the year; if more than 40% of that total went into service in the fourth quarter (October–December for a calendar-year taxpayer), the mid-quarter convention applies to every personal-property asset placed in service that year, not just the fourth-quarter ones.
There is a subtle interaction with bonus depreciation and Section 179: property fully expensed under those provisions is removed from the calculation, which can pull you back under the 40% threshold. In practice, when bonus depreciation is 100%, most short-life property is expensed immediately and the mid-quarter convention rarely bites. But if you elect out of bonus depreciation for a class of assets, the mid-quarter test comes back into play, so run the numbers before making that election.
A mid-quarter example: the same purchase, less deduction
Return to the $10,000 of five-year property, but assume it was your only personal-property purchase of the year and you placed it in service in November — the fourth quarter. Because 100% of your personal property went into service in Q4, well over the 40% threshold, the mid-quarter convention applies. The fourth-quarter, five-year rate is only about 5%, so your first-year deduction drops to roughly $500 instead of the $2,000 you would have gotten under the half-year convention.
That $1,500 difference is pure timing — you recover it in later years — but for an investor counting on a first-year deduction, it is a meaningful swing. The planning takeaway is simple: if you are buying appliances, furniture, or equipment for a rental and you are near year-end, either accelerate some purchases into the third quarter or make sure fourth-quarter purchases stay under 40% of the year's total, so you keep the more generous half-year treatment.
The conventions do not change the total, only the timing
Whichever convention applies, you eventually recover 100% of the asset's depreciable basis — the conventions only shift when the deductions land. Because a deduction taken this year is worth more than the same deduction taken years from now (time value of money), a taxpayer who can use the deduction generally prefers the half-year convention's larger first-year write-off. But the value is real only if you can actually use the loss: for a passive investor whose rental losses are suspended, the timing difference may be nearly irrelevant, since suspended losses carry forward and release at sale regardless.
One more point ties the conventions together: they apply asset by asset and class by class, so a single rental can have its building on the mid-month convention, its appliances on the half-year (or mid-quarter) convention, and its land improvements on their own 15-year schedule — all in the same year. A clean depreciation schedule that records each asset's class, method, convention, and placed-in-service date is what lets your preparer compute year-one depreciation correctly and, years later, figure the recapture when you sell.
How the convention is baked into the MACRS tables
You rarely apply a convention by hand. The IRS publishes MACRS percentage tables (in Publication 946, How To Depreciate Property) with the convention already built into each year's factor. There is a separate table for the half-year convention and a set of quarter-specific tables for the mid-quarter convention, so you pick the table that matches your situation and read the year-one percentage straight off it. This is why the five-year half-year figure is simply 20% — the half-year assumption is already inside that number.
The practical workflow is: determine the asset's MACRS class (5-, 7-, 15-year, etc.), determine which convention applies (half-year unless the 40% fourth-quarter test forces mid-quarter), then read the applicable table. Tax software does this automatically, but understanding which table it is using matters when you place a large asset in service near year-end, because that single choice can move your first-year deduction by thousands of dollars — and it is the one input you can actually control by timing the purchase.
Section 179, bonus depreciation, and the conventions
First-year expensing tools interact with the conventions in a way worth understanding. When you elect Section 179 or take bonus depreciation on an asset, that expensed amount comes off the top before the MACRS convention is applied to any remaining basis. With bonus depreciation at 100%, there is often no remaining basis to depreciate, so the half-year-versus-mid-quarter question becomes moot for that asset — you have already deducted it in full.
This is also why the mid-quarter test can quietly flip on or off. Because property fully expensed under Section 179 or bonus depreciation is removed from the 40% fourth-quarter calculation, heavy year-end purchases that would otherwise trigger the mid-quarter convention frequently do not, once bonus depreciation is applied. If you elect out of bonus depreciation for a class of assets, though, the full basis re-enters the test and the mid-quarter convention can reappear — one more reason to model the election out before making it.
Frequently asked questions
Does the half-year convention apply to rental buildings?
No. Buildings use the mid-month convention, not the half-year convention. The half-year convention applies to personal property (equipment, appliances, furniture).
What triggers the mid-quarter convention?
If more than 40% of the total cost of personal property placed in service during the year was placed in service in the fourth quarter, the mid-quarter convention applies to all personal property placed in service that year.
Can I get a full year of depreciation if I buy an asset January 1?
No. MACRS always applies a convention in year one. Under the half-year convention, you get a half-year regardless of the purchase date.
Sources
Educational information and estimates only. Not tax advice. Tax rules change and vary by situation; consult a qualified tax professional before acting.