One person buys detergent on the way home while another adds it to a delivery. Both noticed it was running low, and neither knew the other had acted.
Choose a shared list that the household can use easily. Add the item when the need becomes clear and mark it when someone is handling the purchase. Include the preferred size or type only where it matters.
Agree on the signal
Decide when an item counts as low enough to add. Keep the arrangement practical for everyone, including anyone who cannot use the chosen app. A visible paper list may work better than a digital system nobody remembers to open.
Before ordering, check what is already stored and what another person has marked as bought. If duplicates keep occurring, inspect the handover step rather than adding more categories. You may need a quick message when an order is placed. Review the list occasionally to remove items that no longer belong in the household's normal shopping.
