Before a state can force you to pay its taxes or collect taxes on its behalf
you must have nexus with that state. Nexus is a minimum link or connection.
When it comes to sales tax you that link must be some sort of physical
presence. However the states have gotten very aggressive in defining what
constitutes physical presences and the US Supreme Court has backed them up in
many cases.

For example the use of third parties or may not even represent you
exclusively can be that "physical presence" that creates nexus. They don't
even have to be permanently located in the state. For example if a third part
travels into the state of Michigan on your behalf and is there for grater
than 1 day then the state of Michigan asserts that is a nexus creating
activity for you.

In the situation where you have a business in MN. You would charge sales tax
on shipments to your customers in MN. In your other 3 states if you have
created nexus you would charge sales tax. Sales tax in interstate
transactions involving tangible property is always based on the ship to
address. So if you don't have nexus you should not charge any tax. Do not
charge MN tax on out of state shipments.

You stated you delivered the product. If you used the US Mail, Fedex, UPS or
a similar service this would not create nexus for you. If you used your own
car or truck it would create nexus for you in most instances. Some other
issues to consider when deciding if you have nexus are; advertising in local
print, radio or TV, having third parties or employees travel into a state on
your behalf and the use of "click trough" relationships on the internet.

Not every state is the same in determining what creates nexus. If you post
your activities in a specif state I will be more than happy to comment on
whether or not the state would assert they are nexus creating.

If you have Nexus in a state, you must collect sales tax.  Nexus is determined differently from state to state.  It depends on what you're selling, distribution methods, physical presence, among other factors.  If sales tax issues are taking a toll on you, you might consider hiring a firm to file multistate sales tax return for you.

IRS releases guidelines for state sales tax deductions, hope this post useful to you - seattlepi.com/money/204327_salestax18.html ---This post was edited to remove a commercial link. Read our discussion policies for more Community best practices.

In most states you collect sales tax only for sales occurring in the state in which your business is physically located, not on sales made in other states. Your state tax commission or revenue department should be able to help you and the information may be on their web site.

Generally, the state where your business was registered (often your home state is where most of your business income is generated. In this case, your home state will tax the bulk of your business income. Other states where you do business will tax the income that you earned in that state. In some cases, your home state may tax all your income and offer a credit for the taxes that you pay to other states. Note that some states do not collect income tax but that doesnt necessarily mean the income is tax-free. Your home states taxation office may require you to report it with them. BizResearch is right - for more detailed tax information, contact the appropriate state department of revenue. You can read more about Doing Business In Multiple States in this Business.gov article.

If you deliver a tangible good, you will need to collect and pay sales tax to the state where the sale is made. For example if you are in MN and sell dog food to an IL customer in IL, you will need to collect and pay sales tax in IL.