Data file conversions What really happens.
There is something that I want to clear up. Especially since I have at times used terms that might confuse the issue, and certainly others seems to have the wrong impression of.
Quicken subscription data files are backwards compatible down to Quicken 2016, but that doesn't imply that the data file format hasn't changed.
Quicken wouldn't be able to add features and such that depend on the changes in the database, unless that database can change.
The trick is how you add those changes. With careful forethought/planning you can put in changes in a way that the old version "doesn't see/ignores" them. The main component of this is to start (say at Quicken 2016) a policy that first if Quicken doesn't recognize a database field, it ignores it. And second that you "add", but never "subtract" fields and such.
The reason I point this out is because as can be seen in several posts it is definitely possible to have "conversion errors". Quicken Subscriptions loading in an older data file, even one that was produced by Quicken 2016 or later, can certainly be changing that data file.
(I'm using the latest Quicken subscription version)