What happens if Required Minimum Distributions (RMD) is not done or amount is wrong?

Question

My wife inherited an IRA from her late mother.  At the time, wife was 66 and MIL was 88.  Another QA says RMD (for MIL) starts at 70½ but the manager of a different investment we have says it starts at 73.  We were told by MIL’s trustee that we are required to withdraw all of it within ten years.  But Edward Jones did not process an amount until we told them to.  Since the value varies, we just took ten percent of the value at that time, and assumed we could take one-ninth, one-eighth, etc. in following years.

Is our method for computing amount valid?  What would be the penalty, if any, if we had not known of the requirement? How would the IRS know if we didn’t do it?

(Not trying to get out of it, since we really don't like Edward Jones.  We're putting the RMDs into a better investment—giving it to the people who would get it anyway if we were dead.)

Related

Answer 1

Your MIL must have started taking RMDs, given that she passed at the age of 88. She must have started taking the RMDs at the age of 70 and a half (it was raised to 73 recently, way past your MIL's RMD start date).

We were told by MIL’s trustee that we are required to withdraw all of it within ten years.

This is not RMD. Your wife has to withdraw everything by the end of the tenth year, she can do it in a lump sum or in partial distributions any time during that period.

See more details at the IRS site here. From the IRS link:

For defined contribution plan participants or IRA owners who die after December 31, 2019, (with a delayed effective date for certain collectively bargained plans), the entire balance of the deceased participant's account must be distributed within ten years. There's an exception for a surviving spouse, a child who has not reached the age of majority, a disabled or chronically ill person, or a person not more than ten years younger than the employee or IRA account owner.

The new 10-year rule applies regardless of whether the participant dies before, on, or after the required beginning date. The required beginning date is the date an account owner must make take their first RMD.

Missed RMDs have a steep 25% excise tax penalty. But it doesn't sound like your wife is required to take RMDs.