Preserve the original calculation
Save the order confirmation showing each item, the total discount, delivery and payment methods. If the shop displays the discount against individual lines, keep that breakdown. If it appears only as one basket-level reduction, retain the offer terms explaining how it is applied.
Record which items you intend to keep and which you are returning. Check whether the promotion was a simple percentage, a fixed basket reduction, a multi-buy or a free-gift threshold. These arrangements can produce different calculations, so a previous return from another order is not a reliable guide.
Use an example to check the arithmetic
Suppose a fictional £100 order contains items at £60 and £40, with a 10% discount allocated proportionally. The discounted line values are £54 and £36. Returning the £40 item would start from its £36 paid value in that example, not its original £40 price.
A fixed £10 discount on the same order needs its own allocation rule. Do not invent an equal split or assume it all belongs to the returned item. Ask for an itemised explanation if the retailer's calculation is unclear. Any promotional adjustment must still be considered alongside applicable consumer rights.
Keep the return connected to the right order
Use the retailer's return reference and identify the exact item, size and quantity. Photograph or note the contents before sealing the parcel, particularly when returning several similar products. Keep the posting receipt and tracking reference with the original invoice.
When the refund notice arrives, compare it with the returned lines, any explained postage charge and the original payment split. A refund to a gift card may appear separately from a card refund. Check both before concluding that money is missing.
If the figures do not reconcile, send a short calculation to the seller with the order and return references. Ask which discount allocation or charge explains the difference. Keeping the query numerical and specific makes it easier to distinguish an administrative error from a condition that needs clarification.
