The first time you set up a plan we would normally advise using last year’s actual data as long as it had a fairly normal business pattern.  For example, the results from 2020 will not be a good base for planning a normal business year and Actual 2019 may need to be used. 

If you prepare frequent (monthly or quarterly) forecasts it may be best to use the last forecast each time.  That way you will start from your latest expectations of pricing and cost levels each time and can just update for the latest developments. 

Note that creating a plan will always fetch the latest consumption/usage data from cockpits so the choice of comparative only affects any prices or splits used to turn the expected volumes into financial plans. 

It is advisable to set up a policy around the comparatives to use in your chain to make different property forecasts more comparable.