If a marketplace like Amazon already collected California tax, do I owe use tax too?

No. Use tax exists specifically to cover the gap when tax wasn't collected at the point of sale. If a marketplace facilitator or an out-of-state retailer already charged you California sales tax, that sale is settled — use tax doesn't stack on top of it.

What if the out-of-state seller charged their own state's sales tax instead?

You can generally claim a credit for sales tax properly paid to another state against the California use tax owed on the same purchase, up to the amount of California's tax. If the other state's rate was lower than California's, you typically owe the difference; if it was equal or higher, you may owe nothing further — but you still need to be able to show what was actually paid.

How do individuals actually calculate what they owe?

For purchases under $1,000, California provides an estimated use tax table based on your adjusted gross income — a simplified lookup rather than tracking every purchase. For any single purchase of $1,000 or more, you calculate the actual amount owed using the use tax worksheet instead of the table. Either way, it goes on Form 540, Line 91 of the personal income tax return.

Why would buying my own resale inventory trigger use tax?

A resale certificate lets you buy inventory tax-free specifically because you're going to charge sales tax when you resell it — you're not the end consumer, so tax isn't due yet. If you instead pull an item out of that inventory for your own use (a bakery owner eating the pastries, a retailer keeping a piece of merchandise for personal use), you've become the end consumer for that item. Use tax is then owed on what you paid for it, measured at the point you converted it to your own use. This exact pattern — resale-certificate purchases quietly diverted to personal use — is one of the more common findings in a CDTFA audit.

What rate applies to a use tax purchase?

The combined rate for the location where you used, stored, or consumed the item — not the out-of-state seller's location, since there usually isn't a California location to source from on their end. A business in a higher-district-tax city owes use tax at that city's combined rate on an untaxed out-of-state purchase used there, the same as it would owe sales tax on an equivalent in-state purchase.

California tax

California Use Tax: What You Owe When Sales Tax Wasn't Collected

Use tax is sales tax's mirror image — same rate, same purpose, but self-assessed by the buyer instead of collected by the seller. It shows up in three places people don't expect: your personal income tax return, your business's regular sales tax return, and an audit of your resale certificate purchases.

6 min read · Published August 2026

Key Takeaways

Use tax applies at the same rate as sales tax, on goods you bought without paying California tax and then used, stored, or consumed in California.
Individuals report it on Form 540, Line 91 — either from an AGI-based lookup table for purchases under $1,000, or a worksheet for larger purchases.
A business with a seller's permit doesn't file a separate use tax return — it's reported as "purchases subject to use tax" on the same periodic sales and use tax return.
The rate that applies is based on where you used the item, not where the out-of-state seller was located — there's no seller location to source from.
Buying inventory tax-free with a resale certificate and then using some of it yourself instead of reselling it triggers use tax on that portion — a common audit finding.

The tax nobody remembers exists — until an audit finds it

Sales tax gets all the attention because sellers collect it visibly, at the register or checkout. Use tax is the quieter companion: the same tax, same rate, owed on the same kinds of purchases — but self-assessed by the buyer when nobody collected it at the point of sale. It exists so that buying from an out-of-state seller who didn’t charge California tax doesn’t become a way to avoid tax entirely.

Use tax isn’t a different tax. It’s sales tax with the collection step missing, made up after the fact.

When it applies

You buy something online or by phone from an out-of-state retailer who doesn’t charge California tax.
You buy equipment or supplies from an out-of-state vendor for business use, and no California tax was charged on the invoice.
You bring goods into California that you bought while traveling, for use here.
You pull inventory out of stock you bought tax-free with a resale certificate, and use it yourself instead of reselling it.

In every case, the common thread is the same: tangible goods ended up being used, stored, or consumed in California without California tax ever being paid on them.

Individuals: Form 540, Line 91

For a personal income tax filer, use tax isn’t a separate return — it’s a single line on the regular California income tax return (Form 540, Line 91). Two ways to calculate what goes there:

Situation	How to calculate
Purchases under $1,000 each	Use the estimated use tax table, based on your California AGI — a simplified lookup instead of tracking every receipt
Any single purchase of $1,000 or more	Use the use tax worksheet to calculate the actual tax owed on that specific purchase

Businesses: no separate filing, just a line on the regular return

A business with a California seller’s permit handles use tax differently — and more simply, in one sense. There’s no separate use tax return to file. Instead, untaxed purchases subject to use tax get reported as “purchases subject to use tax” on the same periodic sales and use tax return the business already files, for the period in which the item was first used, stored, or consumed. It’s one more line item on a return you’re filing anyway, not an extra compliance obligation layered on top.

The resale certificate trap

Buying inventory tax-free with a resale certificate is legitimate — you’re not the end consumer, so tax isn’t due at that point. But the moment you use some of that inventory yourself instead of reselling it (personal use, gifts, samples consumed rather than sold), you’ve become the end consumer for that portion, and use tax is owed on what you paid for it. Auditors specifically look for this pattern — inventory purchased tax-free that never shows up in sales records.

Which rate — and why it’s not the seller’s

Use tax is calculated at the combined rate for where you used, stored, or consumed the item — not the out-of-state seller’s location. This actually makes use tax simpler than the seller-side sourcing question covered in the sourcing article: there’s no California business location on the seller’s end to split the rate against, so the full combined rate — base plus whatever district applies — is just the buyer’s own location, full stop.

Calculate what you’d owe

Same math as sales tax — enter the purchase amount and your local rate.

Calculate the tax

You might also read

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How California Sales Tax Is Actually Calculated: Sourcing Rules and the Weird Stuff

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Are Resale Purchases Exempt From Sales Tax in California?

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How to Register for a California Seller's Permit: The Step-by-Step Setup

The permit itself is free and the online application takes maybe twenty minutes — the parts that actually trip people up are the security deposit, picking the right permit type, and figuring out what happens when you close or sell the business.

Sources & References

Frequently asked

Questions owners actually ask

If a marketplace like Amazon already collected California tax, do I owe use tax too?: No. Use tax exists specifically to cover the gap when tax wasn't collected at the point of sale. If a marketplace facilitator or an out-of-state retailer already charged you California sales tax, that sale is settled — use tax doesn't stack on top of it.
What if the out-of-state seller charged their own state's sales tax instead?: You can generally claim a credit for sales tax properly paid to another state against the California use tax owed on the same purchase, up to the amount of California's tax. If the other state's rate was lower than California's, you typically owe the difference; if it was equal or higher, you may owe nothing further — but you still need to be able to show what was actually paid.
How do individuals actually calculate what they owe?: For purchases under $1,000, California provides an estimated use tax table based on your adjusted gross income — a simplified lookup rather than tracking every purchase. For any single purchase of $1,000 or more, you calculate the actual amount owed using the use tax worksheet instead of the table. Either way, it goes on Form 540, Line 91 of the personal income tax return.
Why would buying my own resale inventory trigger use tax?: A resale certificate lets you buy inventory tax-free specifically because you're going to charge sales tax when you resell it — you're not the end consumer, so tax isn't due yet. If you instead pull an item out of that inventory for your own use (a bakery owner eating the pastries, a retailer keeping a piece of merchandise for personal use), you've become the end consumer for that item. Use tax is then owed on what you paid for it, measured at the point you converted it to your own use. This exact pattern — resale-certificate purchases quietly diverted to personal use — is one of the more common findings in a CDTFA audit.
What rate applies to a use tax purchase?: The combined rate for the location where you used, stored, or consumed the item — not the out-of-state seller's location, since there usually isn't a California location to source from on their end. A business in a higher-district-tax city owes use tax at that city's combined rate on an untaxed out-of-state purchase used there, the same as it would owe sales tax on an equivalent in-state purchase.

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Educational content only. This article is for informational purposes and does not constitute tax, legal, or financial advice. Every situation is different — consult a qualified professional before acting on anything here.