Payback Period is the time it takes for an investment to return its initial cost from the cash flows it generates; a €600,000 project producing €200,000 of net cash a year pays back in three years. With uneven flows, cumulative cash is added year by year and the final year interpolated. The shorter the period, the sooner capital stops being at risk, but the simple version ignores the time value of money, which discounted payback corrects, and both ignore cash after payback. Subscription businesses use CAC payback, the months of gross margin needed to repay customer acquisition cost, read with churn. Acquirers divide purchase price by expected annual free cash flow, comparing it with the revenue-free authorisation period of applying.
How to calculate payback period
With even cash flows, the formula is initial investment ÷ annual net cash flow. With uneven cash flows, add the flows year by year until the cumulative total turns positive, then interpolate within the final year.
A worked example: an EMI spends €900,000 building a card-issuing product. Net cash contribution is €150,000 in year one, €350,000 in year two and €500,000 in year three. After two years, €500,000 has been recovered, leaving €400,000. Year three produces €500,000, so the remainder is recovered in 0.8 of that year. Payback period = 2.8 years.
Discounted payback period
Simple payback treats €1 received in year three as equal to €1 today. Discounted payback first discounts each year's cash flow at the cost of capital. At 12%, the EMI's flows above become about €134,000, €279,000 and €356,000, which total €769,000 after three years. Payback moves beyond year three, and the project that looked like 2.8 years actually needs part of a fourth. If year four also produces €500,000, worth about €318,000 today, discounted payback is about 3.4 years.
Both versions ignore everything after payback. A product that returns its cost in two years and then stops earning scores better than one that pays back in three and earns for ten. That is why payback is used as a risk screen alongside net present value, not as a replacement for it.
CAC payback period
In subscription and fintech businesses, the most common use is CAC payback: the months needed for a new customer's gross margin to repay the customer acquisition cost. If a B2B payments platform spends €6,000 to win a merchant that generates €750 of monthly revenue at 40% gross margin, CAC payback = 6,000 ÷ (750 × 0.40) = 20 months.
CAC payback depends on retention. If the merchant churns at month 14, the cost is never recovered, so analysts read CAC payback with net revenue retention and churn by cohort. Expanding customers shorten real payback; churn lengthens it beyond the formula.
Payback period in M&A
Buyers also calculate payback on the acquisition itself: purchase price ÷ expected annual free cash flow from the target, including synergies. Paying €12 million for a licensed payment institution expected to generate €2 million a year implies a six-year payback before integration costs. For licence acquisitions, the comparison is often with applying from scratch, where the payback clock includes the whole authorisation period with no revenue, which is a large part of the argument for buying.