How capital gains work

A capital gain is the profit from selling something for more than you paid for it. Buy an asset, wait, sell at a higher price, and the difference is yours. It is the oldest mechanic in investing, and the least talkative — nothing about it announces itself until the day you sell.

The arithmetic

Two numbers matter. What you paid, usually called your cost basis, and what you sold for. Sale price minus cost basis equals the gain. Purely hypothetical arithmetic: buy a share at 100, sell it at 130, and the gain is 30. Buying and selling usually cost something too — broker fees come out of that 30, which is why the gain on screen and the gain in your account rarely match exactly.

On paper, then in cash

Until you sell, a gain is unrealised. It exists only as a quote on a screen, and it can shrink or vanish entirely if the price falls back. Having once been up protects nothing. Realising a gain means selling — only then does the number stop moving and become money. The distinction sounds pedantic right up until a paper gain disappears, at which point it becomes the whole point.

Nothing arrives while you wait

Some assets pay their owners along the way: dividends from shares, interest from bonds, rent from property — the full menu is in how people make money from investments. A pure capital gain pays nothing during the holding period. The entire return rests on a single future event: a later buyer agreeing to pay more than you did. A dividend, by contrast, arrives whether or not the share price cooperates. Neither mechanic is superior; they simply fail in different ways — one by being cut, the other by never materialising.

Losses are the same sums, reversed

Sell for less than your cost basis and the arithmetic runs backwards. The same hypothetical share, bought at 100 and sold at 80, produces a loss of 20. Everything above applies in mirror image: a paper loss is not yet real, becomes real when you sell, and no rule says a fallen price must recover. The mechanism that lets prices rise is exactly the mechanism that lets them fall.

Tax, briefly

Most countries tax capital gains, and typically only realised ones — the taxable event is usually the sale, not the price rising while you hold. Rates, allowances and exemptions differ by country and by account type, and they change often enough that any figure printed here would eventually be wrong. The rate tables live with your tax authority, not here.

What this article does not know

Whether any particular asset will produce a gain, when anyone ought to sell, or whether the arithmetic will run in your favour — none of that is knowable from here. This article explains a mechanism: buy, hold, sell, subtract. Everything else depends on prices that have not happened yet, and no article knows those.