How to calculate acquisition payback when customers leave

01

Set the cohort and cost boundary

A cohort is a group acquired in a defined period. Record the number of new customers and the acquisition costs assigned to that group. Contribution is revenue after the selected variable costs of serving those customers. State which costs are included, how discounts and refunds are handled, and whether onboarding is in acquisition cost or contribution. Do not count it twice.

Use consistent periods and include customers after they cancel in the original cohort count. Their future contribution may be zero, negative after a refund, or positive if there are later charges under the agreement. Excluding them because they left makes the remaining average look better than the experience of the group acquired.

A simple CAC divided by steady monthly contribution is an estimate under assumptions. Observed cohort payback instead compares cumulative actual contribution with the cohort's acquisition cost. It is not the same as net profit or the date cash reaches the bank.

02

Calculate cumulative contribution

Suppose ten new customers cost $6,000 to acquire in total. After included variable costs, their combined contribution is $2,000 in month one, $1,600 in month two, $1,200 in month three and $900 in month four. Some customers have left, and those customers remain in the cohort. Cumulative contribution is $2,000, $3,600, $4,800 and $5,700 respectively.

At the end of month four, the cohort is $300 short of acquisition cost, so payback has not yet been reached. If month five adds $500 of contribution, the cumulative total is $6,200 and observed payback occurs in month five. Do not assume that the monthly amount will stay constant to report a payback date before it happens.

If a later refund reduces cumulative contribution below $6,000, show that reversal. Explain whether your policy reports the first crossing or requires a sustained recovery. Both the timing and the later change matter to the decision.

03

Use the result without hiding cash timing

Compare cohorts only with the same acquisition cost boundary, contribution definitions and observation window. Show cohort size, cancellations, cumulative contribution and remaining shortfall. When recent cohorts have not had enough time to recover, mark them as not yet reached instead of comparing their incomplete history with mature cohorts.

Prepare a separate cash view using actual payment and spending dates. Prepayments, late collections and supplier terms can make the bank balance move differently from recognized contribution. If the cohort is small or costs are allocated, show the assumptions and review the underlying records before changing an acquisition budget.