Hello everyone, I am new to Tableau and I know this has been an issue that has been documented multiple times but I have been unable to find a solution for this problem, and I would really appreciate some help. Here is the problem:

I am trying to create a report for retention rate, the methodology of the report is, we start off with a count of distinct companies that had a purchase two years ago. So for example, if we want to measure retention for January 2018, we will first retrieve a count of every unique company that had a purchase from Feb 2016 - Jan 2017. A company is said to be retained FOR JANUARY 2018 if they are in this initial pool of companies AND if they had a purchase in the year following, in this case that would be Feb 2017 - Jan 2018.

I was able to retrieve that initial count of companies with a date parameter ([Choose Date to Look Back]) and filter ([Last 13-24 months: True]). I then created a calculated field to check for retention ([Retention Check]), but I don't think this is right because some companies have multiple [Transaction Date] values. I tried creating another filter ([Last 12 Months]) and moving it to the filter shelf to further the filtering, but that results in 0 companies being shown.

I have attached screenshots of the current view of the report as well as some of the calculations. I am unable to attach a workbook as the datasource contains sensitive client information (apologies for this inconvenience). I have been trying to tackle this problem for days through reading responses from the helpful communities here but unfortunately to no avail. Thank you.