Since the IRS Withholding Calculator is still unavailable as of this writing, I bypassed it and went directly to IRS Notice 1036 (pdf) which is intended to guide employers as to how much to withhold from employee pay. This notice is a typical IRS offering which is both confusing and difficult to understand. I did manage, however, to get the info I needed to proceed with our 2018 withholding “tweaking.”
The financial entity which manages our two pension distributions treats each one as if it were your entire income, thus complicating the final calculation because we actually have several sources of retirement income. Since they are virtually complicating things, I opted out of withholding altogether from the two pensions.
We do, however, have control over the rollover IRA and its exact (to the integer percentage amount) withholding. I figured out what we are paid in each month, cross referenced it to the IRS notice above and determined what we should be sending to the IRS each month.
I have a spreadsheet that I have used in the past for withholding and modified it to determine (to the closest percentage point) what the number should be. I used the “effective tax rate” method based on the numbers I derived to allow me to adjust the withholding from the IRA. This way, I only have one place that I need to be tweaking.
I should have done this last year instead of effectively loaning the .gov interest-free $$$! 🙁