Compare the final cost of offers
A 20% code and a £25 code are not comparable until you know the basket, the threshold and the cap. Final cost means: everything you pay, after every condition you can actually satisfy.
Four figures, in order
Calculate in this sequence and the answer is defensible: pre-discount item total, the extra spend needed to meet a threshold, the discount actually applied after any cap, then delivery and fees. The second figure is the one people forget, and it is often larger than the saving.
A threshold turns a discount into a prompt to spend more. If reaching £150 to save £15 requires £30 of items you did not plan to buy, the offer has cost you money. Write the extra spend in its own column so this is visible rather than arguable.
Two offers compared
Every number here is invented to show the method. Neither offer exists as described.
| Line | Offer A | Offer B |
|---|---|---|
| Basket before discount | £130.00 | £130.00 |
| Threshold | £150.00 | None |
| Extra spend to qualify | £20.00 | £0.00 |
| Discount applied | £24.00 (12% capped) | £15.00 fixed |
| Delivery after any discount | £0.00 | £4.95 |
| Total paid | £126.00 | £119.95 |
Offer A looks like the bigger discount and ends up the more expensive basket, because it required £20 of extra goods. That is the whole argument for a final-cost column.
Fixed, percentage and delivery
A fixed amount favours a small basket: £15 off £50 is a bigger share than £15 off £200. A percentage favours a large basket, until it hits a cap — then it behaves like a fixed amount. A delivery discount only changes the delivery line, so it cannot rescue a basket that is over budget on items.
Stacking and eligibility
Whether two offers combine is a term in the conditions, not a sum you can assume. Record the stacking rule for each coupon in the coupon condition record, and if the wording is silent, treat it as "not confirmed" and model the basket without it.
Then place the confirmed figures into the budget breakdown and check the delivery side against a real quote. When the numbers are ready, the budget tool on the hipobuy spreadsheet home page applies your threshold and cap, shows the arithmetic line by line, and exports it. Finally, keep the terms that govern a return in saving purchase and return conditions.
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