What the checkout estimate includes
The useful checkout answer is usually not just the discounted unit price. The result also shows quantity, total savings and optional tax after discount, which helps when comparing retail prices, ecommerce carts and written quotes.
Example
If an item costs $100 and the discount is 20%, the sale price is $80. Buying 3 items saves $60 before tax; if tax is 7% after the discount, the checkout total is $256.80.
Common mistakes
Apply the discount before tax unless your receipt or local rule states otherwise. Also check whether a coupon excludes sale items, shipping, subscriptions or bundled products.
Assumptions
- Tax is applied after the discount.
- Discounts greater than 100% are rejected.
- Shipping, fees, coupons with exclusions and local tax rules are not included unless you model them separately.
Related formulas
A 20% discount means the customer pays 80% of the original price. For an original price of 100, the sale price is 100 x 0.8 = 80.
References
- Percentage Calculator for the underlying percent logic.
Last reviewed: 2026-05-17