How do I find out if RMD was taken out or not?

Don't you know if you got money from your account?  Did you take a withdrawal?  Did you get a 1099-R?

An RMD is not a specific transaction, it is a minimum amount you must withdraw, based on your age and account balance.  It can be withdrawn any time during the year, and you can always withdraw more, if you want.  Some people who don't need to spend their account on living expenses take the minimum amount at the end of December, but you can withdraw any time.

For example, if your RMD based on your age and account balance is $5000, you would satisfy that by withdrawing $5000 on December 30, or by withdrawing $500 per month all year, or if you withdrew $15,000 in June to buy a car.

If you took a withdrawal but don't know if it was enough to meet your minimum, your broker can tell you what your minimum was for the year.  If you did not take any withdrawal, you may owe a substantial penalty; you would take a withdrawal as soon as you can and then file a form to request a waiver of the penalty.

If you have a traditional pension that ends when you die, you should say yes, it was an RMD, because that's part of how pensions work. 

Did you receive Form 1099-R?

The RMD rules apply to all employer sponsored retirement plans, including

profit-sharing plans, 401(k) plans, 403(b) plans, and 457(b) plans. The RMD rules also apply to traditional IRAs and IRA-based plans such as SEPs, SARSEPs, and SIMPLE IRAs.

The RMD rules also apply to Roth 401(k) accounts. However, the RMD rules do not apply to Roth IRAs while the owner is alive.

Retirement Plan and IRA Required Minimum Distributions FAQs