A replenishment reminder should arrive a few days before a typical customer runs out, point to the exact refill that fits what they bought, and admit you don't know their usage. Start with one product and an interval based on pack size and your own reorder data. Skip anyone who already reordered, returned the item or has an open complaint, and adjust timing from the replies.
Start with one product, not the whole catalog
The temptation is to set one rule ("remind everyone 30 days after purchase") and apply it to everything. Don't. A 250g bag of coffee and a 90-capsule tub of supplements run out at completely different speeds.
Pick the consumable with the clearest repeat pattern. Usually it's your best-selling refillable item. Get that one working, then copy the approach.
For that product, write down three things:
- What they bought (variant, pack size, quantity).
- What they need next (the refill, the same item, or a bigger size).
- What should stop the reminder (a reorder, a return, a subscription, an opt-out).
Match the refill to what they actually own
This sounds obvious. It's where most reminder flows quietly go wrong.
If you sell two dispenser versions and only one takes the new cartridge, a reminder that links to "refills" is a coin flip. If someone bought a sample pack, they probably want the full size, not another sample. If they bought three bags, their timing is different from someone who bought one.
If the mapping between product and refill lives in one person's head, write it down in a sheet before you automate anything. Our guide to helpful cross-sell recommendations covers the same compatibility checks for accessories.
How to choose the reminder interval
Use two inputs:
- The maths. A 500ml bottle at roughly 15ml a day lasts about 33 days.
- Your order history. Look at customers who reordered the product. When did they come back? The middle of that range is a decent starting point.
Then send a few days before that point, not on it. People like a nudge before they run out, not after.
Say you sell a 30-serving tub of protein powder. The maths says 30 days if used daily. Your repeat buyers tend to reorder around day 38, because nobody uses it every single day. A reminder on day 32 is a reasonable first test.
