assuming you're talking about your own IRA or other personal retirement account, the law says that you can wait until the year following the year you turn 70 1/2 to take your first RMD which must be taken by 4/1 of that year. however, you must also take a second RMD by 12/31 of the same year. for example you turn 70 1/2 in 2019. you must take your first RMD by 4/1/20 (this is you 2019 RMD) and a second RMD by 12/31/20 (this is your 2020 RMD). Both are taxed in 2020. As an alternative, you can always take your first RMD any time in 2019, taxable in 2019, and thus you would only be required to take 1 RMD in 2020, taxable in 2020.
Most trustees will notify you of the amount, but in any event it is your responsibility to notify the Trustees to make the RMD and to notify them of any taxes you want withheld. Do not wait until the last minute to notify them. It may take them some time to actually make the distribution,. As a tax preparer for over 40 years, too many times I seen where the request is made in late December and the check is not issued until the following year. Guess what. You have failed to take the RMD for the year in question and are subject to a 50% penalty on the amount not withdrawn. You may be able to escape the penalty by enclosing with the return for that year a reasonable explanation and a promise it won't happen again. However, waiver of these penalties are at the discretion of the IRS.
The Trustee will issue you a 1099-R so you can report the amounts on your tax return. .
