To avoid a penalty you have to make an estimated tax payment by January 15, 2025 to cover the tax on the gain. Your final tax will be calculated on your 2024 tax return, which you have to file by April 15, 2025. If there is still a balance due on your tax return, you have to pay it by April 15.
(You might hear something about an extension for filing your tax return. But an extension only gives you more time to file the return, not to pay the tax. The final tax is due April 15.)
The income will be reported on your 2024 tax return with a deadline for payment on April 15, 2025. Depending upon your other income and withholding you might consider making an estimated tax payment now.
To avoid a penalty you have to make an estimated tax payment by January 15, 2025 to cover the tax on the gain. Your final tax will be calculated on your 2024 tax return, which you have to file by April 15, 2025. If there is still a balance due on your tax return, you have to pay it by April 15.
(You might hear something about an extension for filing your tax return. But an extension only gives you more time to file the return, not to pay the tax. The final tax is due April 15.)