Sales tax is calculated by multiplying your purchase price by the tax rate that applies in your location

The basic formula is simple: purchase price × tax rate = sales tax amount. If you buy something for $100 in a place with a 7% sales tax, you owe $7 in tax, for a total of $107. The complexity comes from the fact that tax rates vary by state, county, and sometimes city — and not all products are taxed the same way.

Your state sets a base rate, but local jurisdictions can add to it. A state might have 5% tax, but your county adds 1% and your city adds 0.5%, making your total rate 6.5%. Some states have no sales tax at all. The rate that applies is the one where the sale physically happens — where you hand over money or pick up the item.

You do not calculate sales tax yourself in most situations. Retailers are required by law to calculate it at checkout and add it to your bill. But if you are a business owner, you need to know how to calculate it correctly so you can charge customers the right amount and send the correct total to your state.

Key Takeaways

  • Sales tax rate depends on the state, county, and sometimes city where the purchase happens, and rates range from 0% to over 10% depending on location.
  • Not all items are taxed: groceries, prescription medications, and some clothing are often exempt, though the rules vary significantly by state.
  • You find your local rate by searching your state's tax department website or your city or county tax assessor's office.
  • If you are a business, you collect tax from customers, hold it in a separate account, and send it to your state on a schedule set by your state (usually monthly or quarterly).
  • Online purchases are now taxed in most states based on where the item ships to, not where the seller is located.

Finding the correct tax rate for your location

Start with your state's Department of Revenue or Department of Taxation website. Every state that has sales tax publishes a rate table or rate finder tool. Search "[your state] sales tax rate" and you will land on the official page. That page will show you the state base rate and usually let you enter your address or zip code to see what local additions apply.

If your state's site is hard to navigate, call your county assessor's office or your city tax office. They can tell you the exact combined rate for your address in under five minutes. Write it down — rates change occasionally, so check again if you are calculating tax for a purchase several months from now.

Some states publish rate tables organized by county and city. Others use a zip code lookup. A few still require you to call. The fastest route is usually the state website's rate finder tool, which asks for your address and returns the number you need.

Understanding what is and is not taxed

Most states exempt certain categories of goods from sales tax. The most common exemptions are groceries (unprepared food), prescription medications, and medical devices. But the rules are not uniform — what is exempt in one state may be taxed in another. Some states tax groceries at a lower rate instead of exempting them entirely.

Clothing is exempt in some states and taxed in others. In a few states, clothing under a certain price point (often $100 per item) is exempt, but more expensive items are taxed. Services are usually not taxed, though some states tax specific services like haircuts or repairs. Digital products like e-books and streaming subscriptions are taxed in some states and not in others.

If you are a business owner, your state's tax department publishes a list of what is and is not taxable. You need to know this list to charge customers correctly. If you are a consumer, the retailer is responsible for charging you the right amount, so you do not need to memorize the rules — but it is worth knowing that if something seems wrong, you can ask the cashier or check your receipt.

How to calculate tax on a single purchase

Take the total price before tax, multiply it by the tax rate as a decimal, and round to the nearest cent. If you buy $50 worth of items in a place with 8.5% tax: $50 × 0.085 = $4.25. Your total is $54.25.

If the math gives you a fraction of a cent, round up or down to the nearest cent. Most states specify rounding rules, but the difference is usually a penny or less. Retailers use point-of-sale systems that do this automatically, so you will never see the unrounded number on a receipt.

If you are buying multiple items with different tax rates (for example, a taxable item and an exempt item), calculate tax on each item separately, then add them together. A $30 shirt taxed at 7% costs $2.10 in tax. A $20 book that is exempt costs $0 in tax. Your total tax is $2.10, and your total bill is $52.10.

Sales tax for online and out-of-state purchases

Online retailers must now collect sales tax in most states, based on where the item ships to, not where the seller is located. If you order something online and it ships to your address, the retailer charges you the tax rate for your location. This rule applies whether the seller is in your state or across the country.

A few small sellers are exempt from collecting tax if they fall below a sales threshold set by their state (often $100,000 or $150,000 per year). But major online retailers like Amazon collect tax on nearly all purchases. If a seller does not collect tax, you may be responsible for paying it yourself to your state as "use tax," though most states do not actively enforce this for individual consumers.

If you buy something in person while traveling to another state, you pay the tax rate of that state. The tax applies where the transaction happens, not where you live. When you bring the item home, you do not owe additional tax to your home state.

How businesses collect and report sales tax

If you own a business, you collect tax from customers at the point of sale and hold it in a separate account. You do not keep this money — it belongs to your state. On a schedule set by your state (usually monthly, quarterly, or annually), you file a sales tax return that shows how much you collected and send that money to your state's tax department.

You will need a sales tax permit from your state before you can legally collect tax. You get this from your state's Department of Revenue. The permit tells you which tax rate to charge and when to file returns. Some states require you to file even if you collected zero tax in a period.

Your point-of-sale system (cash register, online checkout, or accounting software) should calculate tax automatically and track it separately from your other income. At the end of each reporting period, you run a report, verify the total, and send it in. If you make a mistake, you may owe penalties, so accuracy matters.

What happens if the tax rate changes

States and localities change tax rates occasionally. When a rate changes, it usually takes effect on a specific date announced in advance. If you are a business, your state will notify you of the change and tell you when to start using the new rate. You update your point-of-sale system and begin charging the new rate on the effective date.

If you are a consumer, you will simply see the new rate on your receipt after the change date. Retailers are responsible for updating their systems, so you do not need to do anything. If you notice you were charged the wrong rate before the change took effect, contact the retailer — they may issue a refund if the error was on their side.

Some states phase in rate changes gradually or have different rates for different time periods. Your state's tax department website will have the details. If you are a business owner, check your state's site regularly or sign up for email notifications so you do not miss a rate change.

Frequently Asked Questions

Do I have to pay sales tax on everything I buy?

No. Most states exempt groceries, prescription medications, and some medical devices. Many states also exempt clothing, though the rules vary. Services like haircuts and repairs are usually not taxed. Check your state's tax department website for a full list of what is and is not taxed in your area.

Why is the total on my receipt different from what I calculated?

The most common reason is that one or more items in your purchase are exempt from tax. If you bought a shirt and a book, the shirt might be taxed but the book might not be, so the tax is only on the shirt. Check your receipt to see which items show tax and which do not.

What if I buy something online from a seller in another state?

The seller must collect sales tax based on where the item ships to — your state and location. You pay the tax rate that applies where you live, not where the seller is. If the seller does not collect tax, you may owe use tax to your state, though enforcement for individual consumers is rare.

Can I get a refund if I was charged the wrong tax rate?

Yes. If you were charged tax at the wrong rate, contact the retailer with your receipt. Most retailers will issue a refund for the overcharge. If the retailer refuses, you can contact your state's tax department to file a complaint, though this is usually a last resort for larger errors.

How do I know if my business is charging the right tax rate?

Check your state's Department of Revenue website for the current rate in your location. Enter your business address into your state's rate finder tool. Update your point-of-sale system if the rate has changed. If you are unsure, call your state's tax department — they can confirm the rate you should be charging.