> ## Documentation Index > Fetch the complete documentation index at: https://sailia-mintlify-5b02008a.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Stacking and application order > How multiple discounts combine on a booking, and the exact order Sailia uses to calculate the final price. When more than one discount applies to a single item, Sailia follows specific rules about which can coexist and the order the maths runs in. This page explains both. ## Can codes stack? Each discount code has a **Stackable** setting: * **Stackable** — can sit alongside other discounts on the same booking. * **Non-stackable** — if a non-stackable discount is already on the booking, a second one won't apply. Only one non-stackable regular discount can be on a booking at a time. If a customer tries to add a second non-stackable code to a booking that already has one, the second is rejected. Membership discounts are always treated as stackable with regular discounts — they run in a separate layer and don't compete with regular codes. ## Application order When checkout calculates the total for a booking, discounts are applied in this order: 1. **Membership percentage discounts** — taken off the full price first. 2. **Membership fixed discounts** — taken off what's left after step 1. 3. **Regular percentage discounts** — taken off what's left after steps 1–2. 4. **Regular fixed discounts** — taken off what's left after steps 1–3. Each step reduces the price the next step works from. A 10% membership benefit on a £60 booking gives £6 off, leaving £54 — then a £5 regular fixed discount brings it to £49. The total discount can never exceed the original price — you can't discount something below £0. ## Entering multiple codes at checkout A customer can enter several codes if each one passes its own checks. Each code is tested against each booking in the basket — a code might apply to one booking but not another, depending on what it covers and what limits are set. ## Auto-apply and entered codes Auto-apply discounts attach before the customer types anything. When they then enter a code, the stacking rules still apply — a non-stackable manual code won't sit alongside a non-stackable auto-apply discount that's already attached. ## Related guides Fixed, percentage, tiered, auto-apply, and membership types. Add usage, date, and basket conditions to your codes.