I'm not a tax accountant so take this fwiw: it depends, but I'm guessing probably not.
If you operate a business registered in the State of California, and this client is purchasing prints over the internet, and you are shipping prints to him in Missouri, then you do not charge sales tax.
Otherwise if you operate a business that is also registered in the state of Missouri and you are selling prints to a client who resides in Missouri then you must charge Missouri Sales Tax.
Or, If you operate a business registered in the state of California, and this client is purchasing from you in person, then you must charge California sales tax.
It's confusing, but the basic gist is, unless this person is purchasing from you, in California, or you have a business license to operate in MO, you do not charge sales tax.
Consult a professional (or at least the local tax office); California is awash in absolutely ridiculous tax laws.
In general, though, what HinduG has said will be the case: No sales tax if he's buying from Missouri. Missouri would tell you that you need to register and submit tax for Missouri, but states are much more optimistic about who owes them taxes than legal precedent is.
I do know, as a former missouri resident, when Missouri residents file their state income tax returns, are required to report items they bought on the internet, which they were not charged sales tax. So the onus, in this case, would be on your client. However, from watercooler discussions, people rarely report the full amount spent.
If you are selling Prints or items to Out of State and shipping them, there is no sales tax but you have to declare the sale on your Sales Return as Out of State Sales. If the person lives out of State and is picking them up then you have to charge Sales Tax.
I also assume then that you have a valid Sales Permit. If you do not then it is assumed that you do not sell much and then you do not charge Tax.
You can always call the information line on: 800-400-7115 if you have any questions.
Most states are now moving toward what they call "use tax" rather than sales tax. It is really the same thing, but is meant to include items bought elsewhere but "used" in the state. For example, if you live in Washingtonstate and go to Oregon (whiich has no sales tax) jto buy a car, you have to pay WA Use Tax if you bring the car into WA within a year of purchase.
Scor,
You're getting pretty much all the right answers.
I do this nationwide and deal with all kinds of issues. Most states' tax is defined as sales and use tax - hence the reason you pay tax on video rentals - use.
For INTERstate commerce, most states do not require collection of tax without a physical presence in the state. In our case, we are physically present (on-site sales of sporting events) but do not deliver onsite and do not collect tax and are not registered with the state. When we used to print onsite, we registered in 7 states and are pretty much stuck with it and have to now collect on all orders to that state - onsite or online. Then we have to file monthly to quarterly - even if we have no sales. It is a pain in our A$$ every 20th of the month. Missouri is like Georgia too, where you get to DYNAMICALLY calculate the tax based on county - what joy.
If you can (legally) avoid it, try not to be registered with a state.
However, most states would LIKE us to collect tax for them - or at least give them a sales register of customers from their state, so they can demand USE tax from their citizens. Similarily, some states will file that information with other states and overall, the gap is closing on INTERNET sales because the USE tax is so hard to collect and alot of tax money is falling through the borders.
The best advice - since you are asking about this is to contact your DOR and MO's DOR and either get the written dox explaining it and/or ask at least 3 different people, and don't stop until you get a majority concensus as to what the law really stipulates. (seriously, if you ask any 1 person, you may not get accurate information)
