Owing state tax Interest and a result of living in Maryland and working in Virginia
Ultimately, you are the one that is responsible for your tax filings and your payments (It's all linked to your SSN, after all). If this fee/interest is the result of a filing error, and you went through a preparing company which assumes liability for their own errors, then you should speak to them. They will likely correct this and pay the fees.  On the other hand, if this is the result of not making quarterly payments, then you are responsible for it. (Source: Comptroller of Maryland Site) If you [...] do not have Maryland income taxes withheld by an employer, you can make quarterly estimated tax payments as part of a pay-as-you-go plan. If your employer does withhold Maryland taxes from your pay, you may still be required to make quarterly estimated income tax payments if you develop a tax liability that exceeds the amount withheld by your employer by more than $500. From this watered-down public-facing resource, it seems like you'll get hit with fees for not making quarterly payments if your tax liability exceeds $500 beyond what is withheld (currently: $0). The reciprocity agreement in the Washington DC area means that you only pay income taxes where you live, not where you work. Because you live in Maryland you only need to pay income taxes to Maryland. You need to do the following things. Line 3. If you are not subject to Virginia withholding, check the box   on this line. You are not subject to withholding if you meet any one   of the conditions listed below. Form VA-4 must be filed with your   employer for each calendar year for which you claim exemption from   Virginia withholding.  (a) You had no liability for Virginia income tax   last year and you do not expect to have any liability for this year. ... (d) You are a domiciliary or legal resident of   Maryland, Pennsylvania or West Virginia whose only Virginia source   income is from salaries and wages and such salaries and wages are   subject to income taxation by your state of domicile. My company has its only office in Maryland, and conducts all of its   business there. Several of our employees are Virginia residents who   commute to work on a daily basis. Are we required to withhold Virginia   income tax from their wages? No. Because your company is not paying wages to employees for services   performed in Virginia, you are not required to withhold Virginia tax.   If you would like to withhold the tax as a courtesy to your employees,   you may register for a Virginia withholding tax account online or by   submitting a Registration Application. Additional withholding per pay period under agreement with employer.   If you are not having enough tax withheld, you may ask your employer   to withhold more by entering an additional amount on line 2.
Maryland is one of only two states (as of the writing of that article) that collects both inheritance tax and estate tax. These are two different issues, and it's important to differentiate between them sufficiently. I can't provide you a definitive answer, so consult a tax professional in Maryland for specific details to make sure you don't run afoul of tax authorities. This blog has a nice summary of the differences, as of 2012: The estate tax is assessable if more than one million dollars passes at death.  The total dollar value of the property determines whether there is an estate tax.  The inheritance tax is not dependent upon the value of the estate, as even very small estates can have inheritance tax imposed.  Inheritance tax is assessed on property given to a person who is further removed in relationship than a sibling.  Thus, for example, a 10% tax will be assessed on property passing to a cousin, niece, nephew or friend.  Another section of the page states, as an example: If you give someone $10,000 in cash, the inheritance tax will simply reduce the amount inherited – in this case to $9,000. There are several other exemptions to the inheritance tax in addition to the immediate family exception discussed above: Property that passes from a decedent to or for the use of a grandparent, parent, spouse, child or other lineal descendant, spouse of a child or other lineal descendant, stepparent, stepchild, brother or sister of the decedent, or a corporation if all of its stockholders consist of the surviving spouse, parents, stepparents, stepchildren, brothers, sisters, and lineal descendants of the decedent and spouses of the lineal descendants. Putting this information together makes me think that the inheritance wouldn't be taxable in your case because it's a cash inheritance from an immediate family member, so it qualifies for one of the exemptions. Since I'm not a tax professional, however, I can't say that for sure. Hopefully these pages will give you enough of a foundation for when you talk to a professional. "The other answer has mentioned ""factual resident"", and you have raised the existence of a U.S./Canada tax treaty in your comment, and provided a link to a page about determining residency. I'd like to highlight part of the first link: You are a factual resident of Canada for tax purposes if you keep   significant residential ties in Canada while living or travelling   outside the country. The term factual resident means that, although you left Canada, you   are still considered to be a resident of Canada for income tax   purposes. Notes If you have established ties in a country that Canada has a tax treaty   with and you are considered to be a resident of that country, but you   are otherwise a factual resident of Canada, meaning you maintain   significant residential ties with Canada, you may be considered a   deemed non-resident of Canada for tax purposes. [...] I'll emphasize that ""considered to be a resident of Canada for income tax purposes"" means you do need to file Canadian income tax returns. The Notes section does indicate the potential treaty exemption that you mentioned, but it is only a potential exemption. Note the emphasis (theirs, not mine) on the word ""may"" in the last paragraph above. Please don't assume ""may"" is necessarily favorable with respect to your situation. The other side of the ""may"" coin is ""may not"". The Determining your residency status page you mentioned in your comment says this: If you want the Canada Revenue Agency's opinion on your residency   status, complete either Form NR74, Determination of Residency Status   (Entering Canada) or Form NR73, Determination of Residency Status   (Leaving Canada), whichever applies, and send it to the International   and Ottawa Tax Services Office. To get the most accurate opinion,   provide as many details as possible on your form. So, given your ties to Canada, I would suggest that until and unless you have obtained an opinion from the Canada Revenue Agency on your tax status, you would be making a potentially unsafe assumption if you yourself elect not to file your Canadian income tax returns based on your own determination. You could end up liable for penalties and interest if you don't file while you are outside of Canada. Tax residency in Canada is not a simple topic. For instances, let's have a look at S5-F1-C1, Determining an Individual’s Residence Status. It's a long page, but here's one interesting piece:  1.44 The Courts have stated that holders of a United States Permanent Residence Card (otherwise referred to as a Green Card) are   considered to be resident in the United States for purposes of   paragraph 1 of the Residence article of the Canada-U.S. Tax   Convention. For further information, see the Federal Court of Appeal's   comments in Allchin v R, 2004 FCA 206, 2004 DTC 6468.   [...] ... whereas you are in the U.S. on a TN visa, intended to be temporary. So you wouldn't be exempt just on the basis of your visa and the existence of the treaty. The CRA would look at other circumstances. Consider the ""Centre of vital interests test"": Centre of vital interests test [...] “If the individual has a permanent home in both Contracting States, it   is necessary to look at the facts in order to ascertain with which of   the two States his personal and economic relations are closer. Thus,   regard will be had to his family and social relations, his   occupations, his political, cultural or other activities, his place of   business, the place from which he administers his property, etc. The   circumstances must be examined as a whole, but it is nevertheless   obvious that considerations based on the personal acts of the   individual must receive special attention. If a person who has a home   in one State sets up a second in the other State while retaining the   first, the fact that he retains the first in the environment where he   has always lived, where he has worked, and where he has his family and   possessions, can, together with other elements, go to demonstrate that   he has retained his centre of vital interests in the first State.” [emphasis on last sentence is mine] Anyway, I'm acquainted with somebody who left Canada for a few years to work abroad. They assumed that living in the other country for that length of time (>2 years) meant they were non-resident here and so did not have to file. Unfortunately, upon returning to Canada, the CRA deemed them to have been resident all that time based on significant ties maintained, and they subsequently owed many thousands of dollars in back taxes, penalties, and interest. If it were me in a similar situation, I would err on the side of caution and continue to file Canadian income taxes until I got a determination I could count on from the people that make the rules." There are a few methods you can use to estimate your taxes. On the results screen, the app will show you your estimated tax burden, your estimated withholding for the year, and your estimated overpayment/refund or shortfall/tax due.  It may also have recommendations for you on how to adjust your W-4 (although, this late in the year, I think it only tells you to come back next year to reevaluate).   Your state might also have income tax, and if you are curious about that, you can find the state tax form and estimate your state income tax as well. My guess is that you will be getting a refund this year, as you have only worked half of the year.  But that is only a guess. The IRS can direct your refund towards repayment of your unpaid taxes either on Federal or State/Local level. Whether it will depends on whether the State of New York will ask for it. Generally, if you owe taxes to New York for this year only, you would expect them to wait for you to file your State tax return and pay the taxes owed. If you don't - I'm pretty sure that the next year refund from the IRS will go directly to them. There are too many nuances to the question asked to explore fully but here are a few points to keep in mind. If you are a cash-basis taxpayer (most individuals are), then you are not required to pay taxes on the money that has been billed but not received as yet.  If you operate on an accrual basis, then the income accrues to you the day you perform the service and not on the day you bill the client. You can make four equal payments of estimated tax on the due dates, and if these (together with any income tax withholding from wage-paying jobs) are at least 90% of your tax liability for that year, then you owe no penalties for underpayment of tax regardless of how your income varied over the year. If your income does vary considerably over the year (even for people who only have wages but who invest in mutual funds, the income can  vary quite a bit since mutual funds typically declare dividends and capital gains in December), then you can pay different amounts in each quarterly installment of estimated tax. This is called the annualization method (a part of Form 2210 that is best avoided unless you really need to use it).  Your annualized income for the payment due on June 15 is 2.4 = 12/5 times your taxable income through May 31. Thus, on Form 2210, you are allowed to assume that your average monthly taxable income  through May 31 will continue for the rest of the year. You then compute the tax due on that annualized income and you are supposed to have paid at least 45% of that amount by June 15. Similarly for September 15 for which you look at income through August 31, you use a multiplier of 1.5 = 12/8 and need to pay 67.5% of the tax on the annualized income, and so on.  If you miscalculate these numbers and pay too little tax in any installment, then you owe penalties for that quarter.  Most people find that guesstimating the tax due for the entire year and paying it in equal installments is simpler than keeping track of nuances of the annualized method. Even simpler is to pay 100% of last year's tax in four equal installments (110% for high earners) and then no penalty is due at all. If your business is really taking off and your income is going to be substantially higher in one year, then this 100%/110% of last year's tax deal could allow you to postpone a significant chunk of your tax bill till April 15. "Most (if not all states) in the US are only interested in source income. If you worked in that state they want to tax it. Many states have reciprocity agreements with neighboring states to exempt income earned when a person works in lets say Virginia, but lives in a state that touches Virginia.  Most states don't consider interest and dividends for individuals as source income. They don't care where the bank or mutual fund branch is located, or headquartered.If it is interest from a business they will allocate it to the state where the business is located.  If you may ask you to allocate the funds between two states if you move during the year, but most people will just divide the interest and dividends based on the number of days in each state unless there is a way to directly allocate the funds to a particular state.  Consider this: Where is the money when it is in a bank with multiple branches? The money is only electronic, and your actual ""$'s"" may be in a federal reserve branch. Pension funds are invested in projects all over the US." When you pay interest on a loan used to fund a legitimate investment or business activity, that interest becomes an expense that you can deduct against related income. For example, if you borrowed $10k to buy stocks, you could deduct the interest on that $10k loan from investment gains.  In your case, you are borrowing money to invest in the stock of your company.  You would be able to deduct the interest expense against investment gain (like selling stock or receiving dividends), but not from any income from the business. (See this link for more information.) You do not have to pay taxes on the interest paid to your father; that is an expense, not income.  However, your father has to pay taxes on that interest, because that is income for him. "I did a little research and found this article from 2006 by a Villanova law professor, titled ""No Thanks, Uncle Sam, You Can Keep Your Tax Break"".  The final paragraph of the article says: Under these circumstances, it is reasonable to conclude that a taxpayer is not required to claim a allowable deduction unless a statutory provision so requires, or a binding judicial precedent so specifies. It would be unwise, of course, to forego a deduction that the IRS considers mandatory such as those claimed by self-employed individuals with respect to their self-employment,    whether for purposes of the self-employment tax or the earned income tax credit. Until the statute is changed or some other binding authority is issued, there is no reason taxpayers who wish to forego deductions, such as the dependency exemption deduction, should hesitate in doing so. (The self-employment tax issues in the quote cited by CQM are explicitly discussed in the article as one of a few special kinds of deduction which are mandatory.) This is not a binding statement: it's not law or even official IRS policy.  You could never use it as a defense in the event that this professor turned out to be wrong and the IRS decided to go after you anyway.  However, it is a clear statement from a credible, qualified source."