Precedence — which promo wins?

When several promotions could apply:

1. They are checked in Priority order, lowest number first (0 before 1 before 10).
2. Every promotion whose conditions match is applied, so discounts stack by default.
3. If a matching promotion has Stop other rules on, nothing after it is checked.

Catalog promotions change product prices first. Cart promotions then apply to the cart, already using those lower prices.

Avoid surprise double discounts

• Give your main sale a low priority number and switch Stop other rules on, if you don't want coupons on top of it.
• Or add a condition to the coupon so it doesn't apply to sale categories.
• Set a Max Discount Cap on percentage coupons.

Test combinations with a real cart before a big sale: sale price + coupon + free shipping + bank offer can add up quickly.