Expert analysis · reviewed 6 Oct 2026
Inactive customer reactivation: targeting those the offer brings back, not those who would return on their own.
Key distinctions
Three conditions before calculating.
Inactive is a definition, not a state
The inactivity threshold depends on the purchase cycle: three months without an order do not mean the same thing for a monthly subscription and for durable equipment. It is set from the observed intervals between two purchases.
Some inactive customers come back on their own
Recently lapsed customers often return without a reminder. Only a control group separates the returns that were caused from the spontaneous ones.
A reactivated customer is worth their future margin
The gain from a reactivation is the margin brought in after the return, not the return order. A customer who comes back only once with a discount voucher can cost more than they bring in.
Method
Building a measurable reactivation campaign in four steps
- 01Set the inactivity threshold
Measure the distribution of intervals between two purchases and define inactivity beyond an interval that few active customers exceed.
- 02Segment by length of inactivity
Separate customers by the time elapsed since their last purchase and by their past value, because the probability of return declines over time.
- 03Contact with a control group
Randomly exclude a share of each segment from the reminder, to measure spontaneous return.
- 04Value on future margin
Track the margin of reactivated customers over several months and compare it with the cost of the reminders and incentives used.
The real cost of a reactivated customer, segment by segment
Three inactive segments contacted at €4 per customer, with a control group in each. The cost per additionally reactivated customer ranges from €67 to €400.
| Inactive segment | Return with reminder | Return without reminder | Incremental return | Cost per customer contacted | Cost per customer reactivated |
|---|---|---|---|---|---|
| Inactive for 3 to 6 months | 18% | 12% | 6 points | €4 | €67 |
| Inactive for 6 to 12 months | 9% | 4% | 5 points | €4 | €80 |
| Inactive for more than 12 months | 3% | 2% | 1 point | €4 | €400 |
Beyond 12 months, each reactivated customer costs €400: compare this with their future margin and the CAC of a new customer.
A profitable campaign, half as profitable as it looks
Illustrative example: 20,000 customers inactive for 6 to 12 months receive a €10 voucher, and 2,000 others form the control group. The return rate reaches 9% among contacted customers and 4% in the control group. A returning customer generates €45 of margin over the following year.
Additional reactivated customers = 20,000 × (9% − 4%) = 1,000. Margin gained = 1,000 × €45 = €45,000. Vouchers redeemed = 20,000 × 9% × €10 = €18,000. Net effect = 45,000 − 18,000 = €27,000.
The campaign is profitable, but 800 of the 1,800 returning customers would have come back without the voucher. Measured on the raw rate, it would have been credited with €81,000 of margin instead of €45,000.
Acceptance conditions
What must be true to act.
- 01
Define inactivity from observed purchase intervals, not from a fixed duration.
- 02
Hold out a control group in every segment contacted.
- 03
Calculate the cost per additionally reactivated customer, not per returning customer.
- 04
Stop contacting a segment whose cost per reactivated customer exceeds its expected future margin.
Limits
What this analysis does not prove.
- A customer's return may be temporary and may not restore their past purchase frequency.
- Repeated reminders can trigger unsubscribes and reduce the reach of later campaigns.
- The probability of return estimated over one season may change in the next.
- Customers who left after a bad experience need a different response than an incentive.
References
Works cited.
- Thomas, Blattberg & Fox (2004), Recapturing Lost Customers (opens in a new tab)
- Kumar, Bhagwat & Zhang (2015), Regaining “Lost” Customers: The Predictive Power of First-Lifetime Behavior, the Reason for Defection, and the Nature of the Win-Back Offer (opens in a new tab)
- Schmittlein, Morrison & Colombo (1987), Counting Your Customers: Who Are They and What Will They Do Next? (opens in a new tab)