Well, if this has not happened yet, quarter three ended August 31. Any sale that happened between September 1 and December 31 is technically in quarter four** and the estimated payment would be due January 15.
The option which is least likely to result in penalties and extra paperwork, is to pay all the estimated tax in the quarter in which the lump sum income occurs. If you end up overpaying, you would get the difference back as part of your tax refund.
** estimated taxes are not quite due every three months. For income earned from January through March, the due date is April 15. April and May, due date is June 15. June through August, due date is September 15. September through December, due January 15.
