When paying estimated quarterly taxes, can I prorate the amount based on the irregular payment due dates?
Varying the amount to reflect income during the quarter is entirely legitimate -- consider someone like a salesman whose income is partly driven by commissions, and who therefore can't predict the total. The payments are quarterly precisely so you can base them on actual results. Having said that,  I suspect that as long as you show Good Intent they won't quibble if your estimate is off by a few percent. And they'll never complain if you overpay. So it may not be worth the effort to change the payment amount for that last quarter unless the income is very different. "You may want, or at least be thinking of, the annualized method described in Pub 505 http://www.irs.gov/publications/p505/ch02.html#en_US_2015_publink1000194669 (also downloadable in PDF) and referred to in Why are estimated taxes due ""early"" for the 2nd and 3rd quarters only? . This doesn't prorate your payments as such; instead you use your income and deductions etc for each of the 3,2,3,4-month ""quarters"" to compute a prorated tax for the partial year, and pay the excess over the amount already paid. If your income etc amounts are (nearly) the same each month, then this computation will result in payments that are 3,2,3,4/12ths of 90% of your whole-year tax, but not if your amounts vary over the year. If you do use this method (and benefit from it) you MUST file form 2210 schedule AI with your return next filing season to demonstrate that your quarterly computations, and payments, met the requirements. You need to keep good per-period (or per-month) records of all tax-relevant amounts, and don't even try to do this form by hand, it'll drive you nuts; use software or a professional preparer (who also uses software), but I'd expect someone in your situation probably needs to do one of those anyway. But partnership puts a wrinkle on this. As a partner, your taxable income and expense is not necessarily the cash you receive or pay; it is your allocated share of the partnership's income and expenses, whether or not they are distributed to you. A partnership to operate a business (like lawyers, as opposed to an investment partnership) probably distributes the allocated amounts, at least approximately, rather than holding them in the partnership; I expect this is your year-end draw (technically a draw can be any allowed amount, not necessarily the allocated amount). In other words, your husband does earn this money during the year, he just receives it at the end. If the year-end distribution (or allocation if different) is significant (say more than 5% of your total income) and the partnership is not tracking and reporting these amounts (promptly!) for the IRS quarters -- and I suspect that's what they were telling you ""affects other partners"" -- you won't have the data to correctly compute your ""quarterly"" taxes, and may thus subject yourself to penalty for not timely paying enough. If the amount is reasonably predictable you can probably get away with using a conservative (high-side) guess to compute your payments, and then divide the actual full-year amounts on your K-1 over 12 months for 2210-AI; this won't be exactly correct, but unless the partnership business is highly seasonal or volatile it will be close enough the IRS won't waste its time on you. PS- the ""quarters"" are much closer to 13,9,13,17 weeks. But it's months that matter."
Your capital gain is about $40K, which (assuming your total income is under $250K) is taxed at 15% long term capital gains rate. Additional depreciation recapture of approximately $5K is taxed at 25%. So this gives us rough estimate of $7250 tax. This is Federal tax, AZ rates are somewhere between 2% and 4%, so you'll be looking at some $1.6K additional tax to AZ. If you have accumulated rental losses or other expenses, it will lower the total amount of your gain (and, accordingly, the taxes). This is all very rough estimates, and you shouldn't rely on this but verify on your own or with a professional. I suggest using professional services because while being costly, they will probably save you more in taxes than you'll have to pay them because of the knowledge of what exactly of your expenses can be deducted and how to calculate the cost basis correctly. (edit from JoeT - the home exclusion requires occupancy for 2 of prior 5 years. For the OP, the prorated $125k exclusion 'might' cover the gain, it depends when the increase in value occurred, if the gain was during the time rented, it's taxable, I believe.) 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. Do you have a regular job, where you work for somebody else and they pay you a salary? If so, they should be deducting estimated taxes from your paychecks and sending them in to the government. How much they deduct depends on your salary and what you put down on your W-4. Assuming you filled that out accurately, they will withhold an amount that should closely match the taxes you would owe if you took the standard deduction, have no income besides this job, and no unusual deductions. If that's the case, come next April 15 you will probably get a small refund. If you own a small business or are an independent contractor, then you have to estimate the taxes you will owe and make quarterly payments. If you're worried that the amount they're withholding doesn't sound right, then as GradeEhBacon says, get a copy of last year's tax forms (or this year's if they're out by now) -- paper or electronic -- fill them out by estimating what your total income will be for the year, etc, and see what the tax comes out to be. Unless you are getting the loan from a loan shark, it is the most common case that each payment is applied to the interest accrued to date and the rest is applied towards reducing the principal.  So, assuming that fortnightly means 26 equally-spaced payments during the year, the interest accrued at the end of the first fortnight is $660,000 x (0.0575/26) = $1459.62 and so the principal is reduced by $2299.61 - $1459.62 = $839.99 For the next payment, the principal still owing at the beginning of that fortnight will be $660,000-$839.99 = $659,160.01 and the interest accrued will be $659,160.01 x (0.0575/26) = $1457.76 and so slightly more of the principal will be reduced than the $839.99 of the previous payment.  Lather, rinse, repeat until the loan is paid off which should occur at the end of 17.5 years (or after 455 biweekly payments). If the loan rate changes during this time (since you say that this is a variable-rate loan), the numbers quoted above will change too. And no, it is not the case that just %5.75 of the $2300 is interest, and the rest comes off the principle (sic)? Interest is computed on the principal amount still owed ($660,000 for starters and then decreasing fortnightly). not the loan payment amount. Edit  After playing around with a spreadsheet a bit, I found that if  payments are made every two weeks (14 days apart) rather than 26 equally spaced payments in one year as I used above, interest accrues at the rate of 5.75 x (14/365)% for the 14 days rather than at the rate of (5.75/26)% for the time between payments as I used above each 14 days, $2299.56 is paid as the biweekly mortgage payment instead of the $2299.61 stated by the OP, then 455 payments (slightly less than 17.5 calendar years when leap years are taken into account) will pay off the loan.  In fact, that 455-th payment should be reduced by 65 cents.  In view of rounding of fractional cents and the like, I doubt that it would be possible to have the last equal payment reduce the balance to exactly 0. The obligation is contractual, so you need to read the contract to answer your question. However, since you paid for the service provided, I see no way they can force you buy any other service from them. They cannot file your tax returns without your explicit consent (on a form dedicated to that, dated and having the numbers matching the return filed - not something you can sign before the actual return is ready). Worst case they can claim you owe them more money, but since you paid for the services provided, I can't see how they can have that stand in court as well. Bottom line - even if the contract has such an obligation, I cannot see how it can be enforced. As to the mistake they noted... I wouldn't rely on H&R Block advice in any matter. Very likely, the person you were talking to was not even licensed to provide tax advice. You're lucky if the person has passed CRTP exams (in California they're legally required), but I seriously doubt their clerks are EAs or CPAs (the only designations other than a lawyer legally allowed to provide tax advice). Tax preparers (CRTPs included) are only allowed to provide advice pertaining to the preparation of the tax return they're currently engaged to prepare. Claiming income is sourced or not sourced in NY is borderline, IMHO. If they got it wrong (and to me it sounds as they did) you can sue them for damages. If your situation is tricky and it is too late to get an appointment with a proper adviser - file an extension (form 4868) and deal with it after the April busy season. Because the distribution date was APR 21, 2011, THAT should be the correct date for ascertainng the stock prices of the GM stock and warrants.  The subsequent distributions after April should also be allocated in accordance with their distribution dates, with tax basis being reduced from the original APR 21st date's allocations, and reallocated to those subsequent distributions, taking into account any interim sales you might have made. You're interpreting this correctly. Furthermore, if your total tax liability is less than $1000, you can not pay estimates at all, just pay at the tax day. See this safe harbor rule in the IRS publication 17: General rule.    In most cases, you must pay estimated tax for 2016 if   both of the following apply. You expect to owe at least $1,000 in tax for 2016, after subtracting your withholding and refundable credits. You expect your withholding plus your refundable credits to be less than the smaller of: 90% of the tax to be shown on your 2016 tax return, or 100% of the tax shown on your 2015 tax return (but see Special rules for farmers, fishermen, and higher income taxpayers , later).   Your 2015 tax return must cover all 12 months.