Tax withheld on retirement income is considered to have been paid quarterly throughout the year. It works better to take all or most of your RMD near the end of the year when you have a good estimate of your tax liability. Then withhold your tax liability from your last RMD withdrawal. I believe it is the tax withheld from the retirement account that is considered paid quarterly. Estimated payments separate from what is withheld from your RMD might not count. If you depend on your retirement income during the year to the extent that your tax liability can’t be satisfied through your RMD near the end of the year this might not work for you.
