Estimated Taxes Fall Short of tax liability — how do I pay extra online (Federal and NYS)
If you qualify for the safe harbor, you are not required to pay additional quarterly taxes.  Of course, you're still welcome to do so if you're sure you'll owe them; however, you will not be penalized. If your income is over $150k (joint) or $75k (single), your safe harbor is: Estimated tax safe harbor for higher income taxpayers. If your 2014 adjusted gross income was more than $150,000 ($75,000 if you are married filing a separate return), you must pay the smaller of 90% of your expected tax for 2015 or 110% of the tax shown on your 2014 return to avoid an estimated tax penalty. Generally, if you're under that level, the following reasons suggest you will not owe the tax (from the IRS publication 505): The total of your withholding and timely estimated tax payments was at least as much as your 2013 tax. (See Special rules for certain individuals for higher income taxpayers and farmers and fishermen.) The tax balance due on your 2014 return is no more than 10% of your total 2014 tax, and you paid all required estimated tax payments on time. Your total tax for 2014 (defined later) minus your withholding is less than $1,000. You did not have a tax liability for 2013. You did not have any withholding taxes and your current year tax (less any household employment taxes) is less than $1,000. If you paid one-fourth of your last year's taxes (or of 110% of your last-year's taxes) in estimated taxes for each quarter prior to this one, you should be fine as far as penalties go, and can simply add the excess you know you will owe to the next check.
Here is what I was able to find: Yes, but there are special instructions for minors: Working hours: New York State labor laws are slightly more strict than the federal: https://www.labor.state.ny.us/workerprotection/laborstandards/workprot/nyvsfed.shtm Minimum wage: The Dept of Labor's Youth & Labor page states: Occupations such as babysitting are not subject to the minimum wage law. No supporting documentation is given. Another page describes the Youth Minimum Wage Program: A minimum wage of not less than $4.25 may be paid to employees under the age of 20 for their first 90 consecutive calendar days  However, I can't find any such exception in New York State minimum wage law. According to Publication 926, Household Employer's Tax Guide: Federal income tax withholding No, I am not required to withhold federal income taxes from a household employee.  If we both want them to be withheld, a W-4 should be submitted to me. State income tax withholding No, according to NYS Pub 27: Withholding income tax (federal or New York State) from wages paid to household employees is voluntary on your part and your employee Social security and medicare No, I am not required to withhold FICA taxes because when calculated wages, I should not include: An employee who is under the age of 18 at any time during the year.   Exception: Count these wages if providing household services is the   employee's principal occupation. If the employee is a student,   providing household services is not considered to be his or her   principal occupation. Unemployment insurance No, I don't think I have to pay federal unemployment tax.  I think the exception for FICA applies to FUTA.  For New York (according to Household Employers Guide for Unemployment Insurance), there is an exception for paying state unemployment insurance: Daytime students who attend elementary or high school (However, you must pay UI taxes on wages you pay these students if you are liable under FUTA.) I can't find any specific requirements, but aside from numbers of hours times rate of pay, you might want to consider the information required by the Wage Theft Prevention Act: Also, consider this requirements from the NY Minimum Wage Act Every employer shall keep true and accurate records of hours worked by   each employee covered by an hourly minimum wage rate, the wages paid   to all employees, and such other information as the commissioner deems   material and necessary, and shall, on demand, furnish to the   commissioner or his duly authorized representative a sworn statement   of the same. 1040ES uses the smaller number because that's what triggers the penalties.  (That is, you are penalized if what you prepay is less than your total 2013 liability and less than 90% of your 2014 liability.)  However, estimated taxes are just estimates.  If you pay too little, you could face a penalty, but there's no penalty for paying too much -- you'll just get a refund as usual. It seems that your concern stems from the fact that this is the first year you're in this tax situation and so you're unsure if your estimates are accurate.  In your comment to Pete Belford's answer, you also indicated you aren't worried about being unable to pay, but only about accidentally underpaying. In this case, you could just err on the side of caution and pay more than 1040ES says you owe.  (You don't actually file the 1040ES, the calculations are just for your own use.)  For instance, you could prepay based on the higher of your two estimates, if you can afford it; or, if you can't afford that much, hedge the estimate payments up a bit to an amount you can afford that is closer to the higher estimate.  At the end of the year if you paid too much you can get a refund as usual.  After this year, you will presumably have a better sense of your income and your tax liability, and can make more accurate estimates for next year. How much Federal Capital Gains, NYS Income tax and local tax should I expect to pay? You're going to net about 2.4 millions of dollars. Federal long term capital gains tax is 20% (plus 3.8% medicare), NYS is 8.82%. Does it make sense to investigate the tax benefits of financing the sale for the buyer? Yes. Have your tax adviser check the options for you (financing, instalment, etc), especially if you have no other US-sourced income. Tax treaties are also something your tax adviser should be looking at. Be sure your tax adviser is properly licensed in New York as either EA, CPA or Attorney. Don't do anything without a proper tax advice. Tax brackets refer to the range of taxable within which you fall. An income tax bracket usually refers to federal or state tax, not the combined rate. I have put here the tax brackets for 2016 for IRS and State of California.  https://www.irs.com/articles/2016-federal-tax-rates-personal-exemptions-and-standard-deductions  https://www.ftb.ca.gov/forms/2016-california-tax-rates-and-exemptions.shtml According to those, a taxable income of 100,000USD would fall in the 28% bracket for the IRS and 9.30% for State of California. The combined rate is therefore 37.3%. However, this does not mean you would pay 37,300USD. First of all, your applicable tax rate applies only for each dollar in your tax bracket (e.g. 28% * 8,849USD for IRS). Therefore, to calculate your combined taxes you would need to do:  Therefore, your effective tax rate would be much lower than the combined tax rate of 37.3%. Now do note that this is an example to illustrate tax brackets and is nowhere near the amount of taxes you would be required to pay because of various credits and deductions that you would be able to benefit from. Edit: As suggested in the comments, a note on marginal tax rate (referred to here as combined tax rate). This is the rate of taxes paid on an additional dollar of income. Here, every additional dollar of income would be taxed at 37.3%, leaving you with 62.7 cents. In this situation I would recommend figuring out about what you would need to pay in taxes for the year.  You have two figures (your salary and dependents) , but not others.  Will you contribute to a 401K, do you itemize deductions, etc...  If things are uncertain, I would figure my taxes as if I took the standard deduction.   For argument's sake let's assume that comes out to $7300.  I would then add $500 on to my total to cover potential increases in taxes/fees.  You can adjust this up or down based on your ability to absorb having to pay or the uncertainty in your first calcuation. So now $7800, divide by 26 (the amount of paychecks you receive in a year) = $300 Then I would utilize a payroll calculator to adjust my exemptions and additional witholding so my federal withholding is as close as possible to this number.   Or you can sit with your payroll department and do the same. You should look into an LLC.  Its a fairly simple process, and the income simply flows through to your individual return.  It will allow you to deduct supplies and other expenses from that income.  It should also protect you if someone sues you for doing shoddy work (even if the work was fine), although you would need to consult a lawyer to be sure. For last year, it sounds like your taxes were done wrong.  There are very, very few ways that you can end up adding more income and earning less after taxes. I'm tempted to say none, but our tax laws are so complex that I'm sure you can do it somehow. Assuming US/IRS: If you filed on time and paid what you believed was the correct amount, they might be kind and let it go. But don't assume they will. If you can't file on time, you are supposed to file estimated taxes before the deadline, and to make that payment large enough to cover what you are likely to owe them. If there is excess, you get it back when you file the actual forms. If there is a shortfall, you may be charged fees, essentially interest on the money you still owe them calculated from the submission due date. If you fail to file anything before the due date, then the fees/interest surcharge is calculated on the entire amount still due; effectively the same as if you had filled an estimated return erroneously claiming you owed nothing. Note that since the penalty scales with the amount still due, large errors do cost you more than small ones. And before anyone asks: no, the IRS doesn't pay interest if you submit the forms early and they owe you money. I've sometimes wondered whether they're missing a bet there, and if it would be worth rewarding people to file earlier in order to spread out the work a bit better, but until someone sells them on that idea... Whether you're self-employed or not, knowing exactly how much tax you will pay is not always an easy task.  Various actions you can take (e.g., charitable donations, IRA contributions, selling stocks) may increase or reduce your tax liability. One tool I've found useful for estimating federal taxes is the Excel 1040 spreadsheet.  This is a spreadsheet version of the income tax return form.  It is not official and is not created by the IRS, but is maintained as a labor of love by a private individual.  In practice, however, it is pretty much an accurate implementation of the tax calculation algorithms encoded in the tax forms and instructions. The nice thing about it is that it's a spreadsheet.  You can plug numbers into various slots in the spreadsheet and see how they affect your federal tax liability.  (You may also owe state taxes depending on what state you live in.)  Of course, the estimates you get by doing this are only (at most) as accurate as your estimates of the various numbers you plug in.  Still, I think it's a free and useful way to get a ballpark estimate of your tax liability based on numbers that you can more easily estimate (e.g., how much money you expect to earn).