Hi Amiora, To figure your your federal safe harbor for 2018, take a look at line 63 on page 2 of form 1040. this is called total tax. That is your tax for 2017. Now look at line 38 on the same page, adjusted gross income. If your adjusted gross income is less that $150,000 then use the total tax amount on 63 to be your safe harbor. If AGI exceeds $150,000 then take 110% of your total tax to calculate your safe harbor. Make sure you pay these taxes quarterly. If you meet the safe harbor at the end of the year but not during it, then you may get a penalty for underpayment of estimated tax. Alternative way to calculate the safe harbor is to pay 90% of the 2018 tax using the annualized method on form 2210. This is quite complicated to do. Plus the new tax law will shake things up a bit. Hope that helps.