how do i know how much of my distribution was an rmd

To figure out how much of your distribution was an RMD, you can follow these steps:

The following can help determine the payout periods and the amount of your required distribution:

• worksheets to calculate the required amount
• tables to calculate the RMD during the participant or IRA owner’s life:
  • Uniform Lifetime Table – for all unmarried IRA owners calculating their own withdrawals, married owners whose spouses aren’t more than 10 years younger, and married owners whose spouses aren’t the sole beneficiaries of their IRAs
  • Table I (Single Life Expectancy) is used for beneficiaries who are not the spouse of the IRA owner
  • Table II (Joint Life and Last Survivor Expectancy) is used for owners whose spouses are more than 10 years younger and are the IRA’s sole beneficiaries

Or you can use this RMD calculator to simplify this process.