Although I can search for a payment description, and the app will tell me the total payments matching that criteria, there doesn’t seem to be a way to limit this total to a particular time period.
I’ll often want to know e.g. how much I spent with TfL in a month, but currently the only way I can see to do that is export my data as CSV and faff about in a spreadsheet!
I moved away from Nationwide, which had this simple but useful feature.
I can see that maybe the iOS app has extra filtering? I’m on Android. https://monzo.com/blog/2016/06/13/1-5