Stack manufacturer, store and digital coupons to find the final price.
Stacking order decides the final price. A percentage discount applied before fixed-value coupons produces a higher price than the reverse, because the percentage then works on a larger base — which is exactly why most retailers sequence it that way. This follows the common till order: percentage off the list price first, then dollar-value coupons subtracted, with the total floored at zero.
Stacked coupon price
Final price = max(0, list price x (1 - store percent off/100) - manufacturer coupon - digital coupon)
Yes. Percentage discounts applied first yield a higher final price than fixed-value coupons applied first, so the sequence at the till is worth checking on large purchases.
Policies vary. Many retailers permit one of each type per item but block two of the same type, and some exclude promotional prices from further coupons entirely.
Before sales tax, yes. Tax is normally charged on the discounted price, so a lower final price also reduces the tax.