Hired with W-9, will I owe estimated tax quarterly?
You must pay your taxes at the quarterly intervals. For most people the withholding done by their employer satisfies this requirement. However, if your income does not have any withholding (or sufficient), then you must file quarterly estimated tax payments.  Note that if you have a second job that does withhold, then you can adjust your W4 to request further withholding there and possibly reduce the need for estimated payments.  Estimated tax payments also come into play with large investment earnings. The amount that you need to prepay the IRS is impacted by the safe harbor rule, which I am sure others will provide the exact details on.
Yes, you can do what you are contemplating doing, and it works quite well. Just don't get the university's payroll office too riled by going in each June, July, August and September to adjust your payroll withholding! Do it at the end of the summer when perhaps most of your contract income for the year has already been received and you have a fairly good estimate for what your tax bill will be for the coming year. Don't forget to include Social Security and Medicare taxes (both employee's share as well as employer's share) on your contract income in estimating the tax due. The nice thing about paying estimated taxes via payroll deduction is that all that tax money can be counted as having been paid in four equal and timely quarterly payments of estimated tax, regardless of when the money was actually withheld from your university paycheck. You could (if you wanted to, and had a fat salary from the university, heh heh) have all the tax due on your contract income withheld from just your last paycheck of the year! But whether you increase the withholding in August or in December, do remember to change it back after the last paycheck of the year has been received so that next year's withholding starts out at a more mellow pace. I will answer this question broadly for various jurisdictions, and also specifically for the US, given the OP's tax home: Generally, for any tax jurisdiction If your tax system relies on periodic prepayments through the year, and a final top-up/refund at the end of the year (ie: basically every country), you have 3 theoretical goals with how much you pre-pay: Specifically, for the U.S. All information gathered from here: https://www.irs.gov/businesses/small-businesses-self-employed/estimated-taxes. In short, depending on your circumstance, you may need to pay quarterly estimated tax payments to avoid penalties on April 15th. Even if you won't be penalized, you, may benefit from doing so anyway (to force yourself to save the money necessary by April 15th).  I have translated the general goals above, into US-specific advice: In short, I suggest you take a look at your W-4 form and adjust it properly. And yes you can claim your self as a dependent, unless someone else is claiming you. But here is a more detailed explanation of how it works. How Income Tax Works. While most people tend to only think about the tax system and the Internal Revenue Service (IRS) as the month of April approaches, it's actually a never-ending process. For our purposes, a good way to explain how the system works is to give an example of one American income earner, we will call him Joe. The tax process begins when Joe starts his new job. He and his employer agree on his compensation, which will be figured into his gross income at the end of the year. One of the first things he has to do when he's hired is fill out all of his tax forms, including a W-4 form. The W-4 form lists all of Joe's withholding allowance information, such as his number of dependents and child care expenses. The information on this form tells your employer just how much money it needs to withhold from your paycheck for federal income tax. The IRS says that you should check this form each year, as your tax situation may change from year to year. Once Joe is hired and given a salary, he can estimate how much he will pay in taxes for the year. Here's the formula: At the end of each pay period, Joe's company takes the withheld money, along with all of withheld tax money from all of its employees, and deposits the money in a Federal Reserve Bank. This is how the government maintains a steady stream of income while also drawing interest on your tax dollars. Toward the end of the tax year, Joe's company has to send him a W-2 form in the mail. This happens by January 31. This form details how much money Joe made during the last year and how much federal tax was withheld from his income. This information can also be found on Joe's last paycheck of the year, but he'll need to send the W-2 to the IRS for processing purposes. At some point between the time Joe receives his W-2 and April 15, Joe will have to fill out and return his taxes to one of the IRS service and processing centers. Once the IRS receives Joe's tax returns, an IRS employee keys in every piece of information on Joe's tax forms. This information is then stored in large magnetic tape machines. If Joe is due a tax refund, he is sent a check in the mail in the next few weeks. If Joe uses e-File or TeleFile, his refund can be direct-deposited into his bank account. "You file taxes as usual. W2 is a form given to you, you don't need to fill it. Similarly, 1099. Both report moneys paid to you by your employers. W2 is for actual employer (the one where you're on the payroll), 1099 is for contractors (where you invoice the entity you provide services to and get paid per contract). You need to look at form 1040 and its instructions as to how exactly to fill it. That would be the annual tax return. It has various schedules (A, B, C, D, E, F, H, etc) which you should familiarize yourself with, and various additional forms that you attach to it. If you're self employed, you're expected  to make quarterly estimate payments, but if you're a salaried employee you can instruct your employer to withhold the amounts you expect to owe for taxes from your salary, instead. If you're using a tax preparation software (like TurboTax or TaxAct), it will ""interview"" you to get all the needed information and provide you with the forms filled accordingly. Alternatively you can pay someone to prepare the tax return for you." Since you both are members of the LLC - it is not a single-member LLC, thus you have to file the tax return on behalf of the LLC (I'm guessing you didn't elect corporate treatment, so you would be filing 1065, which is the default). You need to file form 4868 on behalf of yourselves as individuals, and form 7004 on behalf of the LLC as the partnership. Since the LLC is disregarded (unless you explicitly chose it not to be, which seems not to be the case) the taxes will in fact flow to your individual return(s), but the LLC will have to file the informational return on form 1065 and distribute K-1 forms to each of you. So you wouldn't pay additional estimated taxes with the extension, as you don't pay any taxes with the form 1065 itself. If you need a help understanding all that and filling the forms - do talk to a professional (EA or CPA licensed in your state). Also, reconsider not sending any payment. I suggest sending $1 with the extension form even if you expect a refund. Assuming you are Resident Indian. As per Indian Income Tax  As per section 208 every person whose estimated tax liability for the year exceeds Rs.   10,000, shall pay his tax in advance in the form of “advance tax”. Thus, any taxpayer   whose estimated tax liability for the year exceeds Rs. 10,000 has to pay his tax in   advance by the due dates prescribed in this regard. However, as per section 207, a   resident senior citizen (i.e., an individual of the age of 60 years or above) not having any income from business or profession is not liable to pay advance tax.   In other words, if a person satisfies the following conditions, he will not be liable to pay advance tax:   Hence only self assessment tax need to be paid without any interest. Refer the full guideline on Income tax website The only way you will incur underpayment penalties is if you withhold less than 90% of the current year's tax liability or 100% of last years tax liability (whichever is smaller).  So as long as your total tax liability last year (not what you paid at filing, but what you paid for the whole year) was more than $1,234, you should not have any penalty. What you pay (or get back) when you file will be your total tax liability less what was withheld. For example, you had $1,234 withheld from your pay for taxes.  If after deduction and other factors, your tax liability is $1,345, you will owe $111 when you file.  On the other hand, if your tax liability is only $1,000, you'll get a refund of $234 when you file, since you've had more withheld that what you owe. Since your income was only for part of the year, and tax tables assume that you make that much for the whole year, I would suspect that you over-withheld during your internship, which would offset the lack of withholding on the other $6,000 in income. "My employer decided to pay my salary in India after I submit a form W-8BEN. This means that the wages / salary is deemed accrued for work from India. Hence your employer need not withhold and pay taxes on this wage in US. Is this payment taxable in the States since I am staying outside of States? Should I declare this income to IRS in case if I go back to the States later this year? No tax is due as the work is done outside on US. If you go back this would be similar to as you had gone first. Depending on your ""tax residency status"" you would have to declare all assets. If my US employer wires my US salary to my NRE account is that taxable in India? This is still taxable in India. It is advised that you have the funds transferred into a regular savings account. Please note you have to pay taxes in advance as per prescribed due dates in Sept, Dec, March. how does the Indian tax man identify if it is a taxable income and not just the regular remittance. This question is off topic here. Whether income taxes finds out about this is irrelevant. By law one is required to pay taxes on income earned in India."