GP MoM% =
VAR __PREV_MONTH = CALCULATE([GP], DATEADD('Calendar'[Date], -1, MONTH))
DIVIDE([GP] - __PREV_MONTH, __PREV_MONTH)
However if I look at the end of a month at a daily granularity, say for ex 30 & 31st May its calculating a percentage for both using the Value of April 30th as there is no April 31st. Should it not be blank instead?