The IRS treats bitcoin and other cryptocurrency transactions as property and not as currency. As such, you must figure gain on the transaction in the same way as with any other type of property. The IRS posted guidance (https://www.irs.gov/pub/irs-drop/n-14-21.pdf) on this matter several years ago, but may revisit the topic, so stay alert.
Advance payment of current tax liability based either on wage withholdings or installment payments of your estimated tax liability. To avoid penalties, you generally must pay to the IRS either 90% of your final tax liability, or either 100% or 110% of the prior year’s tax liability, depending on your adjusted gross income.