Payback period is the time a spend takes to earn back what it cost.
A van costing thirty thousand that produces a thousand a month in additional margin pays back in thirty months.
Why a small business often cares about this more than return
Return on investment answers how much. Payback answers how long the business is exposed.
For a business with limited cash, exposure is the binding constraint. A high return that pays back over five years can still be the wrong decision if the business cannot survive the wait — see cash runway.
Short payback is also a hedge against being wrong. The sooner the money is back, the less it matters that the forecast was optimistic.
Calculating it
The cost, divided by the additional margin per period — not the additional revenue. Revenue arrives with its own costs attached.
Where the return is uneven, it is counted period by period until the cumulative margin covers the cost.
What it ignores
Everything after payback. Two purchases paying back in two years are treated identically even if one then produces for a decade and the other is worn out.
So it is a constraint rather than a decision: use payback to rule out what the business cannot afford to wait for, then use return to choose among what is left.
Financed purchases
Where the purchase is financed, the comparison is between the additional margin and the payment — see equipment financing.
An asset whose payment exceeds the margin it generates consumes cash every month it is owned, regardless of what the eventual return looks like.