Should I be filling out form W-9 for somebody I sold used equipment to?
They are a business. You're not a corporation. They paid you more than $600 during the year, so they're supposed to send 1099 to you and the IRS about it. They need your taxpayer certification (W9) for that. They were supposed to ask for it before they paid you, but yes - they're supposed to ask for it.
There are many different types of 1099 forms. Since you are comparing it to a W-2, I'm assuming you are talking about a 1099-MISC form.  Independent contractor income If you are a worker earning a salary or wage, your employer reports   your annual earnings at year-end on Form W-2. However, if you are an   independent contractor or self-employed you will receive a Form   1099-MISC from each client that pays you at least $600 during the tax   year. For example, if you are a freelance writer, consultant or   artist, you hire yourself out to individuals or companies on a   contract basis. The income you receive from each job you take should   be reported to you on Form 1099-MISC. When you prepare your tax   return, the IRS requires you to report all of this income and pay   income tax on it. So even if you receive a 1099-MISC form, you are required to pay taxes on it. "Well, as you say, the instructions for form W-2 (for your employer to fill out) say You must report all employer contributions (including   an employee's contributions through a cafeteria plan) to   an HSA in box 12 of Form W-2 with code W. Employer   contributions to an HSA that are not excludable from the   income of the employee also must be reported in boxes 1,   3, and 5. However, while it's your employer's job to fill out W-2 correctly, it's only your job to file your taxes correctly. Especially as you say your box 1/3/5 income is correct, this isn't too hard to do. You should file Form 8889 with your return and report the contributions on Line 9 as Employer Contributions. (And as you say, both what the employer contributed outright and what you had deducted from your pay are both Employer Contributions.) Be sure to keep your final pay stub for the year (or other documentation) showing that your employer did contribute that amount, just in case the IRS does end up questioning it for some reason.  If you really want to, you could try calling the IRS and letting them know that you have contributions that weren't reported on your W-2 to see if they want to follow up with your employer about correcting their documentation, if your efforts have been fruitless. There's even a FAQ page on the IRS site about how to contact them when your employer isn't giving you a correct W-2 and how to fill out a Form 4852 instead of using the W-2, which I'd recommend if the amount of income listed was wrong or if there were some other more ""major"" problem with the form. Most likely, though, since it's not going to affect the amount of tax anybody will pay, it's not going to be at the top of their list. I would worry more filling out the forms you need to fill out correctly rather than worrying about the forms your employer isn't filling out correctly." "Read up on filing an ""amended tax return"".  Essentially you'll fill out the entire return as it should have been originally, then fill out form 1040X stating what has changed (and pay the additional tax due if needed).   According to TurboTax's website, they have partnered with Sprintax for non-resident tax prep.  I am not vouching for the service; just offering it as information." "For example, for my employer I received a signing bonus, and a   ""relocation lump sum"" separate from that signing bonus. The relocation   lump sum is taxed and will appear as income on my W-2, and I can spend   it on anything I want. That said, should the relocation lump sum count   towards the entry quoted above in Form 3903, or would it be considered   the same as any other bonus; thus allowing me to take a full deduction   for all of my deductible travel expenses? The signing bonus and relocation lump sum will appear as regular income on your W-2. You can think of the relocation bonus as something to cover the pain and suffering the cost of moving, without needing to send in receipts. Lets assume that you meet the distance and time tests, so there is potential to save money on your taxes. Lets also put your actual moving expenses as $2500. If you have valid moving expenses the IRS will allow you to use them to reduce your AGI. So now you can reduce your AGI by the $2500.  Enter the total amount your employer paid you for the expenses listed   on lines 1 and 2 that is not included in box 1 of your Form W-2   (wages). This amount should be shown in box 12 of your Form W-2 with   code P. My question is: what exact payments from your employer should be   entered here? I realize that you can just write the number you get in   box 12 with code P on your W-2, but I'm curious how they come up with   this number. In some cases the company will reimburse you your moving expenses up to a maximum of $x. For example a maximum of $1000 That means you submit receipts for those expenses and they give you a check or add it to your next paycheck. The check will either be for the amount on your receipts or the maximum amount, whichever is smaller. In this situation with actual expenses of $2500 and a reimbursement of $1000 you can reduce your AGI by $1500." "I'm no lawyer and no expert, so take my remarks as entertainment only. Also see this question. If you have a U.S. SSN which is eligible for work, they may be able to pay you on 1099 basis with your SSN as a sole proprietor, unless they have some personal reason for avoiding that. So perhaps try asking about that specifically. HR policies can be weird and tricky, maybe a nudge in the right direction will help. Not What You Asked: regardless, I might recommend you register as an LLC and get an EIN (sort of SSN for companies) for a variety of reasons. It's called a ""limited liability"" company for a reason. You may also have an easier time reaping various business-related rewards, like writing off expenses. If you do so, consider a state with no income tax like Wyoming. (Or, for convenience sake, WA if you live in BC, or maybe NH if you live in Ontario.. etc.)" Why would the IRS be coming after you if you reported the income? If you reported everything, then the IRS will use the 1099 to cross-check, see that everything is in order, be happy and done with it. The lady was supposed to give you the 1099 by the end of January, and she may be penalized by the IRS for being late, but as long as you/wifey reported all the income - you're fine. It was supposed to be reported on Schedule C or as miscellaneous income on line 21 (schedule C sounds more suitable as it seems that your wifey is in a cleaning business). But there's no difference in how you report whether you got 1099 or not, so if you reported - you should be fine. Am I required to send form 1099 to non-US citizens who are not even residing in the US? Since they're not required to file US taxes, do I still have to send the form to them? That's tricky. You need to get W8/W9 from them, and act accordingly. You may need to withhold 30% (or different percentage, depending on tax treaty they claim on W8). If you withhold taxes, you also need to file form 1042. I suggest you talk to a tax professional. Is it fine to expose my ITIN (taxpayer identification number) to   individuals or companies who I send the form to them. Since the form   requires me to write my TIN/EIN, what would be the risks of this and   what precautions should be taken to avoid inappropriate/illegal use? No, it is not OK. But if you pay these people directly - you don't have much choice, so deal with it. Get a good insurance for identity theft, and don't transact with people you don't trust. One alternative would be to pay through a payment processor (Paypal or credit cards) - see your next question. I send payments via PayPal and wire transfer. Should I send form   1099-MISC or 1099-K? Paypal is a corporation, so you don't need to send 1099 to Paypal. Whatever Paypal sends to others - it will issue the appropriate forms. Similarly if you use a credit card for payment. When you send money through Paypal - you don't send money directly to your business counterparts. You send money to Paypal. From the 1099 instructions: File Form 1099-MISC, Miscellaneous Income, for each person to whom you have paid during the year Your accounting method doesn't matter. You file 1099 for the year you paid the money.