Define the cohort, cycle and commitment
Inputs to freeze before calculation
- Choose a starting cohort and state exactly when a subscriber enters it. (not complete)
- Choose a finite number of billing/fulfilment cycles and declare whether churn occurs before or after each shipment. The worked example uses end-of-cycle churn after the current shipment. (not complete)
- Keep subscriber churn, revenue churn, failed payments, pauses, refunds and new additions separate. (not complete)
- Record committed boxes or component-equivalent boxes by supplier commitment date, not only by delivery date. (not complete)
- Record cash cost per committed box on one currency and indirect-tax basis. (not complete)
- Classify excess components as reusable, returnable, markdown-dependent, perishable or custom before assigning recovery. (not complete)
| Input | Unit | Evidence class | Do not confuse with |
|---|---|---|---|
| Starting subscribers | subscribers at cycle start | Reconciled billing/cohort record | All active accounts across different cohorts; in this example they receive the current cycle shipment |
| Subscriber churn scenario | subscriber cancellations/cycle as decimal | Completed cohort record or user scenario | Revenue churn, a forecast or a pre-shipment cancellation in this example |
| Required boxes | boxes/current cycle | Starting subscribers plus any explicit current-cycle allowance | Next-cycle continuing subscribers |
| Committed boxes | boxes/cycle | Purchase order or explicit supplier scenario | Boxes merely planned but cancellable |
| Cash cost per box | currency units/committed box | Current supplier and landed-cost record | Selling price or contribution |
| Excess boxes | committed boxes - required boxes | Calculated scenario output | Automatic economic loss |
Carry the cohort through a finite horizon
Continuing subscribers next cycle = starting subscribers this cycle - churned subscribers + explicitly entered additions
- starting subscribers this cycle
- Eligible subscribers at the declared cycle start who receive that cycle’s shipment in this example (subscribers) — reconciled cohort record or prior-cycle output
- churned subscribers
- Completed subscriber churn events applied after the current cycle shipment in this example (subscribers/cycle) — cohort record or user-entered scenario
- explicitly entered additions
- New subscribers intentionally included in the scenario (subscribers/cycle) — observed additions or separate user scenario
Current-cycle required boxes equal starting subscribers plus any explicit current-cycle replacement allowance. Apply the churn formula after shipment to create the next cycle’s starting cohort. This worked example rounds each calculated churn count to the nearest whole subscriber, with an exact half rounded up, before subtracting it from the cycle start. Do not silently offset churn with forecast additions.
Excess boxes = max(0, committed boxes - required boxes); gross cash exposed = excess boxes × cash cost per committed box
- committed boxes
- Boxes or component-equivalent boxes no longer cancellable for the cycle (boxes/cycle) — purchase order or supplier commitment record
- required boxes
- Boxes shipped to starting subscribers in the current cycle plus any named current-cycle replacement allowance (boxes/cycle) — calculated scenario plus explicit allowance
- cash cost per committed box
- Supplier, inbound and other included cash cost on the declared basis (currency units/box) — current contract and landed-cost record
Gross cash exposed is not final loss. Reusable components, cancellations, later sales, refunds, markdowns and disposal need separate evidenced rows.
- Freeze the starting cohort, cycle dates, finite horizon and whether churn occurs before or after shipment. Use one convention throughout.
- Reconcile committed boxes and supplier cash dates for each cycle.
- Set current-cycle required boxes from the subscribers eligible for that shipment.
- Apply post-shipment churn and additions to calculate the next cycle’s starting subscribers. Record the deterministic whole-subscriber rounding convention.
- Compare current required boxes with non-cancellable committed boxes.
- Calculate gross cash exposed for excess boxes, then classify possible recovery separately.
- Run a lower-retention and a supplier-flexibility sensitivity without treating either as a forecast.
- Carry dated cash into the cash forecast and set a commitment review trigger.
Work the cohort and inventory rows together
Fictional three-cycle subscription-box commitment
The scenario starts with 100 subscribers and no additions. Each calculated churn count is rounded to the nearest whole subscriber, with an exact half rounded up: for example, 8.1 becomes 8 and 12.8 becomes 13. Starting subscribers receive the current cycle box; churn occurs after shipment and determines the next cycle’s starting cohort. Committed boxes and 22 CU cash cost per box are invented user inputs, not provider terms.
| Cycle | Starting subscribers | Current boxes required | Post-shipment churn | Next-cycle continuing | Committed boxes | Excess boxes | Gross cash exposed |
|---|---|---|---|---|---|---|---|
| 1 | 100 | 100 | 10 | 90 | 100 | 0 | 0 CU |
| 2 | 90 | 90 | 9 | 81 | 95 | 5 | 5 × 22 = 110 CU |
| 3 | 81 | 81 | 8 | 73 | 90 | 9 | 9 × 22 = 198 CU |
| Cycle | Starting subscribers | Current boxes required | Post-shipment churn | Next-cycle continuing | Committed boxes | Excess boxes | Gross cash exposed |
|---|---|---|---|---|---|---|---|
| 1 | 100 | 100 | 20 | 80 | 100 | 0 | 0 CU |
| 2 | 80 | 80 | 16 | 64 | 95 | 15 | 15 × 22 = 330 CU |
| 3 | 64 | 64 | 13 | 51 | 90 | 26 | 26 × 22 = 572 CU |
| Inventory class | Evidence to collect | Scenario treatment |
|---|---|---|
| Reusable components | Shelf life, alternate product use and next confirmed cycle | Keep gross cash exposed visible; add recovery only when supportable. |
| Supplier-returnable | Current return right, fee, date and approved quantity | Record expected cash date separately from the gross commitment. |
| Custom or perishable | Expiry, disposal, markdown or alternate-channel evidence | Use a bounded recovery case; never assume full resale. |
Stress the assumptions that can change the decision
| Driver | Scenario change | What to recalculate | Limitation |
|---|---|---|---|
| Subscriber retention | Higher churn by cycle | Continuing subscribers, required boxes and excess boxes | Not a prediction or causal conclusion |
| New additions | Observed or separately entered additions | Required boxes and acquisition economics | Do not use additions to hide churn |
| Supplier flexibility | Later cut-off, smaller minimum or cancellation right | Committed boxes and dated cash | Only current written terms count |
| Inventory recovery | Reuse, later sale, supplier return or disposal | Recoverable value and recovery date | Gross exposure is not automatically loss |
| Per-box contribution | Product, fulfilment, shipping, fee or refund change | Delivered-box contribution and cohort-cycle profit | Positive delivered margin does not erase excess inventory |
- Mixing subscriber churn, revenue churn and failed-payment rate.
- Applying churn before and after the same cycle shipment.
- Netting forecast additions against churn without showing both rows.
- Treating every planned box as contractually committed.
- Calling excess-box cash exposure a realised loss before recovery is assessed.
- Assuming leftover components are reusable without shelf-life or alternate-use evidence.
- Copying a provider churn, fulfilment or payment rate into a Global article.
- Using positive per-box contribution as proof that the inventory commitment is safe.
Route each result to the next decision
Test unit economics, churn and buying capacity
- Subscription Box Profitability & Unit Economics Planner
Test per-box and multi-cycle economics after fulfilment, churn and acquisition burden
- Subscription Churn Impact Planner
Keep logo and revenue churn separate while estimating annual contribution and replacement acquisition impact
- Open-to-buy Planner
Set a buying budget from planned sales, markdowns and stock targets
Commitment review record
- Save the cohort definition, cycle dates and churn-event convention. (not complete)
- Record the exact supplier cut-off and cash dates for each commitment. (not complete)
- Run delivered-box unit economics separately from excess inventory exposure. (not complete)
- Classify recovery evidence by component or finished box. (not complete)
- Put committed supplier payments into the dated cash forecast. (not complete)
- Set a review trigger before the next non-cancellable commitment, not after the inventory arrives. (not complete)
Subscription inventory questions
- Can a profitable box still create an inventory problem?
- Yes. Delivered boxes can retain contribution while churn leaves other committed boxes or components unused and cash exposed.
- What churn rate should the scenario use?
- Use a completed, consistently defined cohort or an explicitly labelled sensitivity. Margin101 supplies no normal or target churn rate.
- Should expected new subscribers offset churn?
- Only as a separate additions row with its own evidence and acquisition economics. Do not hide retention weakness inside a net subscriber number.
- Is gross cash exposed on excess boxes the final loss?
- No. It is a liquidity view. Recovery, reuse, supplier return, markdown, disposal and timing determine the later economic outcome.
- Does this guide recommend how many boxes to order?
- No. It exposes cohort and commitment mismatches. The registered tools, current supplier terms and authorised business decision own the next step.
Methodology and cohort sources
- Subscription Box Profitability methodology — Margin101: Product-owned per-box, finite-cycle, churn and acquisition-cost boundary.
- Subscription Churn Impact methodology — Margin101: Product-owned subscriber/revenue churn separation and finite impact boundary.
- Open-to-Buy methodology — Margin101: Product-owned buying-capacity and commitment workflow.
- Subscriber cohorts and cohort retention in Billing — Stripe Support: Official provider terminology context for explicit cohort assignment and observation; no provider metric or churn benchmark is used.