A thousand dollars today is worth more than a thousand dollars in a year. This is not a statement about inflation, though inflation makes it worse. It is true even with stable prices, for two reasons that are worth separating.

The money can be doing something. A thousand dollars now can be spent, lent, invested or used to buy something that earns. That forgone use is a real cost of waiting, and it is opportunity cost with a clock on it.

The money might not arrive. A promise of a thousand dollars in a year is a promise, and promises fail. The payer can go under, change their mind, or dispute the terms.

Both mean the same thing in practice: future money has to be marked down before it can be compared with present money.

The mechanics, briefly

Discounting reverses compound growth. If money can reliably earn 8% a year, then $1,000 a year from now is worth $1,000 ÷ 1.08 = $926 today, because $926 invested now becomes $1,000 in a year. Two years out, divide twice: $857. Ten years out, the same $1,000 is worth $463.

That last figure is the one worth sitting with. At an unremarkable rate, money a decade away is worth less than half its face value — which is why long-dated promises are worth so much less than they sound, and why anyone offering you one is usually aware of this and hoping you are not.

The rate used is the argument. It should reflect what you could actually do with the money and how likely the payment is. For a small business owner with a productive use for cash and a counterparty who might not pay, the honest rate is considerably higher than a savings account, which makes the discount larger.

Where it actually bites

Payment terms. Ninety days is not the same price as thirty. A 2% discount for paying immediately is, annualized, an enormous rate — and businesses routinely take it without calculating, or refuse it without calculating.

Earn-outs and deferred consideration. A business sold for $500,000 with $200,000 paid over three years contingent on performance is not a $500,000 sale. It is $300,000 plus a discounted, risk-adjusted claim on $200,000, and the honest figure is often nearer $400,000. This is the single most common place the principle is ignored, because the headline number is the one people repeat.

Retainers against project fees. A retainer paying $2,000 a month for a year is worth less than $24,000 today, and a project paying $22,000 up front may be the better deal even though it is a smaller number. See payback period, which is the same insight applied to acquisition spending.

Any decision to wait. Deferring a price rise for six months to avoid an awkward conversation has a cost, and the cost is the six months of the increase, compounded forward for as long as the business runs.

The trap in the other direction

Discounting can be used to justify almost anything, because the rate is chosen. Pick a high enough discount rate and every long-term investment looks bad; pick a low enough one and every deferred promise looks fine. A discounted cash flow with a rate chosen after the answer was decided is arithmetic in the service of a conclusion.

The defense is to state the rate first, in the open, with the reason. "I am discounting this at 15% because that is what I can earn reinvesting in the business, and because I think there is a real chance this payment does not arrive" is a claim that can be argued with. A present value with no stated rate is not.

Why it belongs next to expected value

The two do different jobs and are constantly confused. Expected value handles uncertainty about whether — the probability the money arrives. The time value of money handles when — the cost of it arriving later. A deferred, uncertain payment needs both: discount it for time, weight it for probability, and only then compare.

Doing one and not the other is how a staged deal gets talked about as though it were cash.