I have tried the sumOver function before and it did not generate the expected output (I got £495000 instead of £8,773).
I suspect that this is due to QS calculating 1500 - (value) on a daily basis using “dt” as reference (“dt” has over 1000 records) and then summing them all.

What I am looking for is for QS to perform the following at once :

Summing all the value within a month to get “sub-total 1”,

then minus the monthly “sub-total 1” from 1500 to get “sub-total 2” and

finally adding up only “sub-total 2” to get a single total amount or runningSum

I also tried “runningSum(sum(1500 -{value}), [truncDate(“MM”,{Date}) ASC], [{qs_year}])” but encountered the following issue:

as a workaround, I created a calculated field parsing the Year portion of “dt” but doing so generated the wrong output again (I got £495000 instead of £8,773).

Any further assistance on this will be greatly appreciated.