The new requirement for W-4P is likely due to the changes to the W-4 form for employees, which eliminates the option to claim a certain number of allowances and instead focuses on the employee's actual tax liability. It sounds like you may be concerned about the change to your withholding from your pension, and you're looking for ways to adjust your withholding.
Regarding your question, you can ask your IRA custodian to withhold a certain amount of money from your required minimum distributions (RMDs) if they have the capability to do so. However, you should keep in mind that the withholding is not the same as estimated tax payments and is not credited towards your final tax liability. Also, IRA custodians have different policies regarding withholding, so it's best to check with yours to see if they have this option.
Regarding social security withholding, you can request that a certain amount of money be withheld from your benefits each month. The Social Security Administration has a Form W-4V, Voluntary Withholding Request, which you can use to request withholding from your Social Security benefits.
If you can't adjust your withholding via pension, IRA and SS, you can make estimated tax payments to avoid underpayment penalty.
It's important to note that it's always a good idea to review your withholding and estimated tax payments throughout the year to ensure that you're having the right amount withheld to avoid underpayment penalty. It's recommended that you consult with a tax professional to help you determine the correct amount to have withheld or to make estimated tax payments in order to avoid any penalties.
Based on the information you've provided, it sounds like your total tax liability for the year may exceed $1,000. In that case, you may be required to make estimated tax payments to avoid underpayment penalty.
The IRS generally requires taxpayers to make estimated tax payments if they expect to owe at least $1,000 in taxes for the year, and if they expect their withholding and credits to be less than the smaller of:
90% of the tax to be shown on the return for the current year, or
100% of the tax shown on the return for the preceding year. To calculate your estimated taxes, you can use the IRS's estimated tax worksheet or use the IRS's withholding calculator. This will give you an idea of how much you should be paying in estimated taxes.
It's also important to note that, if you are required to make estimated tax payments and fail to do so, you may be subject to an underpayment penalty.