@samike - A few ways I can think of achieving this..
- Use the recurring revenue report in HubSpot: Track recurring revenue in HubSpot
- Build a dataset to calculate the number of months between the billing start date and today’s date and multiple the line items MRR by this: Create and use datasets
- Create a custom-coded workflow action that calculates the time in months between the ‘Billing start date’ and ‘Today’s date’ and copies the value across to a custom ‘Months active’ number property. Create a calculation property that multiples the value in ‘Months active’ and the value in the ‘MRR’: Create workflows & Create calculation properties
N.B Option 2 & 3 require use to create a ‘Today’s date’ property that enrolls into a workflow every day and stamps the property with the date of the step.