Retirement tax questions

Be aware that for a lump sum of income paid to you in December 2023, an estimated payment would be due January 15, 2024, unless you file your final return by January 31 and include full payment.  Also, the IRS assumes that income is earned evenly over the year and that tax payments should also be evenly spread out.  So even though a lump sum income is paid in December, the IRS will expect to see estimated tax payments in April 2023, June 2023, September 2023, and then the last payment in January 2024.  You can mitigate this on your tax return by including form 2210 (the penalty calculation) and using the "annualized" method, which shows the IRS the quarterly breakdown of your income and that the tax for each quarter was appropriate at the time.