To calculate a combined sales-tax rate, add the individual percentage rates when they all apply to the same taxable amount. Apply the resulting combined percentage to the taxable price to calculate the total sales tax.
Add tax to a price or extract included tax using the percentage rate you provide.
Rates of 5 percent, 2 percent, and 1 percent create a combined sales-tax rate of 8 percent.
Combined Sales-Tax Rate Formula
Add the individual percentage rates when each rate applies to the same taxable amount.
The result is one combined percentage that can be entered into the Sales Tax Calculator.
Do not combine rates this way when they apply to different taxable bases.
Worked Combined-Rate Example
Suppose three applicable rates are 5 percent, 2 percent, and 1 percent.
Adding them gives a combined rate of 8 percent.
On a taxable price of $200, the total tax is $16.
Step-by-Step Method
Confirm that every rate applies to the same transaction amount.
- 1List the applicable rates
Keep the percentage values in the same units.
- 2Add the rates
Combine the percentage values into one total rate.
- 3Apply the combined rate
Multiply the taxable price by the combined rate divided by 100.
- 4Add tax to the price
Add the calculated tax to the taxable amount.
Calculating Each Rate Separately
You can also calculate every tax component separately.
For a $200 price, 5 percent produces $10, 2 percent produces $4, and 1 percent produces $2.
The separate tax amounts total $16, matching the combined-rate result.
Combined Rate Multiplier
Convert the combined rate to decimal form and add one.
An 8 percent combined rate creates a multiplier of 1.08.
Multiplying $200 by 1.08 gives a final price of $216.
Decimal Combined Rates
Rates can include decimal percentages.
For example, 4.5 percent plus 2.25 percent plus 1 percent equals 7.75 percent.
Convert 7.75 percent to 0.0775 before multiplying.
When Rates Should Not Be Added
Do not add rates when they apply to different items, categories, or taxable bases.
A rate on one item and a different rate on another should be calculated separately.
The same applies when one charge is exempt or excluded from a particular rate.
Tax Applied on Top of Another Tax
Simple addition assumes every rate is calculated from the same original taxable amount.
When one percentage is applied after another amount has already been added, the result may be compounded.
Follow the calculation sequence required by the transaction rather than assuming addition is always correct.
Combined Rates and Multiple Items
Group items that share the same set of applicable rates.
Apply the combined percentage to each appropriate taxable group.
Read How to Calculate Sales Tax on Multiple Items for mixed baskets.
Reverse Calculation with a Combined Rate
A tax-inclusive total can be reversed using the combined rate.
Divide the final total by one plus the combined decimal rate.
Subtract the recovered pre-tax amount to find the included combined tax.
Common Mistakes
Do not multiply the individual rates together when they share one taxable base.
Do not combine percentages that apply to different items or amounts.
Do not ignore whether one rate is compounded on top of another.
Conclusion
Add percentage rates when they all apply to the same taxable base.
Apply the combined rate to the taxable price using the ordinary sales-tax formula.
Enter the resulting percentage into the Sales Tax Calculator.
FAQs
How do I combine sales-tax rates?
Add the percentage rates when they apply to the same taxable amount.
What is 5 percent plus 2 percent plus 1 percent?
The combined rate is 8 percent.
Should different item rates be averaged?
No. Calculate separate taxable groups.
Can I reverse a combined tax rate?
Yes. Divide the inclusive total by one plus the combined decimal rate.
Are combined rates ever compounded?
They can be when one charge is applied after another, so calculation rules must be checked.
These examples explain percentage calculations only. Tax rates, exemptions, taxable amounts, discount treatment, service charges, and rounding methods vary. Confirm the current requirements that apply to the transaction.