I claimed 0 allowances, but yet I owe $13k to irs. I am single, no children, live in NYC ...I don't understand why I owe vs getting a refund, I've always gotten refund.

Before any other comments or questions—have you entered ALL of your income yet? The calculations cannot possibly be accurate until all of your income has been entered.

No one on Answer Xchange can see your tax return. There are major tax law changes that have begun with this tax year.  One thing that may be affecting your refund for 2018 is that employers began withholding less tax when the new tax law passed.  Your paychecks were more, but that means a smaller refund now.  There are are lot of variables that affect your refund or tax due including how much you earned, how much tax you had withheld, your filing status, the number of dependents you claim, your deductions and credits, etc.  You may have lost Earned Income Credit or the Child Tax Credit— did a child turn 17?  If you received the EIC last year, remember that changes in the amount you earn have a big effect on the amount of EIC you can get. (Sometimes earning more money means less EIC)  Are you 65 or older ?  If so, your standard deduction is higher. Everyone has a higher standard deduction now so it is harder to use itemized deductions.  Or do you have a healthcare penalty?  We used to be able to suggest comparing two years of tax returns side by side to find the differences.  But with the drastic change in the 2017 and 2018 forms, that is tricky this year.

https://ttlc.intuit.com/questions/4482394-how-will-tax-reform-affect-my-2018-federal-tax-return

And of course, always check your own data entries, looking for errors such as misplaced decimals or extra zeros.

https://ttlc.intuit.com/questions/1901008-why-did-my-refund-go-down-compared-to-last-year-s