Depreciation and amortization, explained without the jargon

You buy a $12,000 set of laptops for the team in March. Your bookkeeper expenses the whole thing that month, and suddenly March looks like a disaster while every other month looks artificially great. Nothing about the business actually changed — only the way the cost landed on the page. Depreciation exists to fix exactly this kind of distortion, and once you understand it, your financials stop lying to you about how a given month really went.

Depreciation is simply the practice of spreading a big asset's cost across the years you'll actually use it, instead of dumping the entire cost into the month you bought it. The laptops don't lose all their value the day they arrive — they earn their keep over years of work, so their cost should show up over those same years.

Amortization is the exact same idea applied to intangible assets — things you can't physically touch, like purchased software, a patent, or goodwill from buying another company. Same logic, different label. The distinction is mostly vocabulary: you depreciate a truck, you amortize a software license, but in both cases you're slicing one big cost into smaller, honest pieces over time.

Why it exists: keeping profit honest

The reason accountants do this comes down to one rule called the matching principle — the idea that you should record an expense in the same period that the thing it paid for actually helps you earn money. A $12,000 laptop fleet that serves you for three years shouldn't punish one month's profit and flatter the other thirty-five.

Get this wrong and every decision built on your numbers gets shaky. You might think a slow month was a problem when it was just a big purchase, or assume a strong month proves a trend when it was only the absence of one. Depreciation smooths that noise so the profit you see reflects how the business is genuinely performing.

Where it actually shows up

Depreciation touches two of your statements at once, and seeing how is what makes it click. On your P&L (profit and loss statement — your monthly record of revenue minus expenses), a slice called depreciation expense shows up each period, quietly reducing profit by a little.

On your balance sheet (the snapshot of what you own and owe), the asset is recorded at full cost, but a running tally called accumulated depreciation sits right beneath it, growing each month. Subtract one from the other and you get the asset's book value — roughly what it's still worth to you. After two years, those $12,000 laptops carry $8,000 of accumulated depreciation, leaving a $4,000 book value.

The worked example and the default method

Take the laptops over a three-year useful life. The simplest and most common approach is straight-line depreciation — you spread the cost evenly across every period. The math is plain: $12,000 divided by 3 years is $4,000 per year, or about $333 per month.

Compare the two ways of recording it:

• Expense it all at once: March takes a $12,000 hit and looks like a terrible month, while the next 35 months look better than they really were.
• Depreciate it straight-line: every month from purchase onward carries a steady $333, and no single month gets distorted.
• The result: your profit reflects operations, not the accident of when you happened to swipe the card.

Straight-line is the sensible default for most small companies. It's predictable, easy to explain, and it keeps your books readable — which matters more than chasing precision you don't need.

Thresholds, and where to hand it to a pro

You don't want to depreciate a $40 keyboard over five years — the bookkeeping isn't worth it. That's why most companies set a capitalization threshold, also called a de minimis policy: a dollar line, often around $2,500, below which you just expense the item outright and move on. Anything above the line gets capitalized and depreciated; anything below gets written off immediately. Pick a threshold, write it down, and apply it consistently.

One important caution: the depreciation on your books and the depreciation you claim on your taxes are often two different numbers. Tax rules offer accelerated breaks — things like Section 179 and bonus depreciation that let you deduct much more upfront — and the available amounts change year to year. Keep your books clean and steady, and let your tax advisor handle the tax version; check current limits with them rather than assuming last year's rules still apply.

Your next step is small: set a written capitalization threshold for your company, make sure straight-line depreciation is running on every asset above it, and ask your accountant to confirm your tax treatment separately. That one hour of housekeeping is what turns your monthly numbers into something you can actually trust.