Nate - If you are writing in the US, live in the US and producing the work that creates the income in the US, then you file it all as your income on Schedule C. For your state and local, include it wherever your state and local dictate self-employment income should be recorded (they all differ).
PGK's situation is different because the property producing the income is located in another country. That sets forth a whole different set of rules. What you are doing is no different that filing income on an ebay store that may sell to other countries. You've essentially retailed your product. The buyer is inconsequential.
BTW - I am a degreed accountant with over 20 years of tax prep. If you're not sure how to complete all the forms, then I suggest you talk to a tax professional the first year, at least to get an idea on all the allowed deductions. If you already have a good idea what to deduct, then something as simple as TurboTax will walk you through all the steps of completing your return.
Nate - The income only becomes an issue if the property producing it (in this case, you) is located in another country. If you move to New Zealand, please talk to an accountant experienced with ex-patriot tax law. Ex-patriot tax law applies to American citizens living abroad and it's a whole separate set of tax rules. Make sure you talk to someone who does that as their main job as it changes all the time and you don't want bad information.
I have sold foreign rights to other countries, independent of publisher distribution, and I file the advances/royalties on my Schedule C along with everything else.
Congrats on your foreign sales and good luck with the move, if you decide to go that route!
If the UK company bought your book through a subsidiary in the US, they may pay the income in the US, which is simpler for you.
If the company pays you in England, and you are a US citizen living in the US, you are responsible for UK taxes on the writing income.
You also pay US taxes on your writing income, starting with the first dollar.
But . . . you get to deduct the Foreign Taxes paid as a Foreign Tax Credit against the taxes you pay in the US. See IRS Publication 514. Here.
The income will be listed on your Federal Income Tax, so you'll pay the usual state and local taxes on it.
I'd ask, nate. I am paid for everything but one through the US. So are most of my friends.
job - I know there are some countries that still require their pint of blood, but in those cases, tax paperwork is usually provided to the author, no? That has been mine and my friend's experience. The tax was withheld from distributions and essentially a non-issue beyond filling out some forms.
This is theoretical- well sort of. If the company is worldwide, and has offices in the U.S, do you think they would be willing to pay through the U.S office to make it easier??? The foriegn door just happened to be open. Of course, I'll have to talk to my agent about this.
Thoughts about taxes takes the wind out of the sails. But it's something that has to be face, and I appreciate your advice.