This oversight (no matter who is to blame) will create a penalty of 50% tax on the amount of the withdrawal which should have been taken. In other words if the RMD was to have been $10,000 and only $6,000 was taken, the penalty imposed by the IRS would be $2,000. This is calculated by taking the amount which should’ve been $10,000 and the actual amount of $6,000 the difference being $4,000. The penalty is 50% of the $4,000 which is $2,000.