A capital expenditure, often shortened to CapEx, is money you spend to buy a long-lived asset or to materially extend the life of one you already own, like a new roof, an HVAC system, or a kitchen remodel. Unlike an ordinary repair, a capital expenditure is not deducted in the year you pay for it; you add it to the property's basis and recover the cost over years through depreciation.
In practice
Say you own a single-family rental and the roof finally gives out. You pay $14,000 to replace it in March. That $14,000 is a capital expenditure, not a repair, because a full roof replacement betters the property and lengthens its useful life. You do not write off $14,000 against this year's rent. Instead the roof becomes a depreciable improvement, recovered on a straight-line schedule over 27.5 years using the mid-month convention.
The yearly write-off is small: roughly $14,000 ÷ 27.5, which is about $509 in a full year, and less in the first year because the mid-month rule counts a partial month for March. Compare that to a $400 repair to patch a leak, which you would deduct in full this year. Same roof, very different timing. That timing difference is the whole reason the repairs versus improvements line matters so much at tax time.
Why it matters to a small landlord
CapEx bites in two places. First, it distorts your year if you treat it like a regular expense: a $14,000 roof booked as a repair can turn a profitable year into a paper loss and invite a closer look from the IRS. The cleaner path is to flag it as capital and let it ride the depreciation schedule, which is exactly what the 27.5-year depreciation math governs. Second, big-ticket items do not announce themselves on a convenient schedule, so you want money set aside before the roof leaks. Budgeting a fixed amount per door each month into cash reserves turns a five-figure surprise into a planned withdrawal.
Most landlords underestimate how often CapEx shows up across a portfolio. One roof, one furnace, and one water heater over a decade is normal, and each one is thousands of dollars that never touched your operating math.
Keep CapEx separate from the costs that recur every month. A roof is a capital improvement; the gutter cleaning that protects it is part of your operating expenses; and the money you parked to pay for the roof lives in your reserves. Get those three buckets right and your books, your taxes, and your cash plan all line up.