You may owe federal income tax when you file your income tax return unless you make estimated tax payments. You may also owe a penalty for underpayment of estimated tax (see below for information about avoiding the penalty).
You can avoid a penalty for underpayment of estimated tax if you owe less than $1,000 in tax for 2019, or if you pay at least 90% of the tax owed for 2019 or 100% of the tax shown on your return for 2018, whichever is smaller.
See https://www.irs.gov/businesses/small-businesses-self-employed/estimated-taxes
