IRA Beneficiary: Calculating required distributions
I understand that required distributions are calculated based on dividing the the balance by life expectancy. My assumption has been that the balance figure used is the ending balance for the prior year. For example, to calculate the distributions required in 2018, the ending balance for 2017 is used.
Is it necessary to adjust distributions during the year if the balance increases significantly? Using the example above, if the balance increases 20% during 2018, even after distributions, is additional distribution required before the end of 2018 to meed minimum distribution requirements?
Thanks in advance for any clarification.