I am in research of these two questions. I found some answers but my question now is: do these case apply to a corporation taxation too? or these answers are only for independent consultant? Please help me to solve these issues. Below are questions and the answers I found so far.

Q1: Do the company have to claim other states as worked?

Most people in the U.S. live and work in the same state, which makes state taxes pretty easy to understand. You pay taxes to that same state where you live and work.

But what if you live in one state and work in another? Do you pay taxes to the state where you live or the state where you make your money?

That answer is that you need to pay taxes to both. Most likely you will end up having to file a resident return in the state where you live and a nonresident return in the state where you work.

Resident return

Generally, you need to file a resident return in the state where you are a permanent resident. This state has the right to tax ALL of your income, wherever it was earned.

Nonresident return

After you file your resident return in your home state, you then need to go about filing a nonresident return in every other state where you earned money. A nonresident return only taxes you on the money you earned in that state.

Lets say you live in New Jersey and every day you commute to your job in New York. In this case you would need to file a resident return in NJ (on all of your income) and a nonresident return in NY (only on the income you earned in NY). You will have an opportunity to claim a credit for taxes paid to the other state. They will then divide whatever has been withheld between them and at the end the state whose liability was not exactly met will either give you a refund or a tax bill.

States without an income tax

The exception to all this is the seven states without an income tax:

• Alaska,
• Florida
• Nevada
• South Dakota
• Texas
• Washington
• Wyoming

In addition, Tennessee and New Hampshire tax only interest and dividends.

If you live in one of these states, you dont need to file a resident return (unless you live in TN or NH and have interest and dividends income). But if you work in a state that does have an income tax you have to file a nonresident return in that state.

The same holds true when the situation is reversed. If you live in a state with an income tax, you must file a resident return there. But if you work in a state without an income tax, you dont have to worry about filing a nonresident return.

Q2: How about if the employee travel to foreign countries and earn money?

Yes, United States citizen & resident aliens are taxed on their worldwide income, whether the person lives inside or outside of the U.S.

If you are a U.S. citizen or resident alien, you must report income from all sources within and outside of the U.S. This is true whether or not you receive a Form W-2 Wage and Tax Statement, a Form 1099 (Information Return) or the foreign equivalents.

Additionally, if you are a U.S. citizen or resident alien, the rules for filing income, estate and gift tax returns and for paying estimated tax are generally the same whether you are living in the U.S. or abroad.

Hiding Income Offshore

Not reporting income from foreign sources may be a crime. The IRS and its international partners are pursuing those who hide income or assets offshore to evade taxes. Specially trained IRS examiners focus on aggressive international tax planning, including the abusive use of entities and structures established in foreign jurisdictions. The goal is to ensure U.S. citizens and residents are accurately reporting their income and paying the correct tax.