You find a $120 jacket on sale for 25% off. You live in a state with 9% combined sales tax. What do you actually pay? Most people either guess or wait for the register to tell them. This guide walks through the exact sequence -- and explains why the order of operations matters more than most shoppers realize.
Step 1: Apply the Discount to the Original Price
Discounts are always applied before tax. This is standard in the US and required by law in most states -- retailers cannot legally charge tax on the pre-discount price when a discount reduces the transaction price.
Formula: Discounted Price = Original Price x (1 - Discount Rate)
For the $120 jacket at 25% off: $120 x (1 - 0.25) = $120 x 0.75 = $90.00
The $90 is now your taxable base.
Step 2: Apply Sales Tax to the Discounted Price
Formula: Final Price = Discounted Price x (1 + Tax Rate)
At 9% tax on $90: $90 x 1.09 = $98.10
Your true checkout cost is $98.10 -- not $87.00 (which is what you'd get if you naively subtracted 25% and ignored tax), and not $130.80 (what you'd get if you added tax before the discount).
Why the Order Matters
Applying tax before the discount would give: $120 x 1.09 = $130.80, then $130.80 x 0.75 = $98.10. Same result in this case -- mathematically, discount-then-tax and tax-then-discount produce the same final price when both are applied to the full original. The reason order matters in practice is when a coupon or promo code is applied to a cart that already includes tax at the item level, which some checkout systems do incorrectly. If you ever see a tax charge that seems too high, check whether it was computed on the pre-discount price.
Stacked Discounts: Two Percentage Discounts Don't Add
If an item is already 20% off and you have a coupon for an extra 15% off, the combined discount is not 35%.
Formula: Final Price = Original x (1 - Discount1) x (1 - Discount2)
$100 item, 20% off, then 15% off: $100 x 0.80 x 0.85 = $68.00. The effective discount is 32%, not 35%. Then add tax: $68.00 x 1.09 = $74.12.
The gap between 35% perceived and 32% actual is $3 on $100. On a $1,000 appliance it is $30. Worth knowing before deciding a price is within budget.
Quick Reference: What You Actually Pay
| Original Price | Discount | After Discount | At 7% Tax | At 9% Tax |
|---|---|---|---|---|
| $50 | 10% | $45.00 | $48.15 | $49.05 |
| $80 | 20% | $64.00 | $68.48 | $69.76 |
| $120 | 25% | $90.00 | $96.30 | $98.10 |
| $200 | 30% | $140.00 | $149.80 | $152.60 |
| $500 | 40% | $300.00 | $321.00 | $327.00 |
For Sellers: Does the Discount Still Leave You Profitable?
If you are a seller running a promotion, the relevant question is whether your margin survives the discount. The sequence is: calculate the discounted price, subtract your cost, then check the margin.
Example: You sell a product for $80 with a $48 cost. You run a 20% off sale. Discounted price: $64. Profit: $64 - $48 = $16. Margin: $16 / $64 x 100 = 25%. Before the sale your margin was ($80 - $48) / $80 = 40%. The 20% price discount cut your margin by 15 percentage points. Use our Margin Calculator to find the minimum price you can sell at while staying above a target margin, and our Discount Calculator to find the discounted price in one step.