What happens to custom field data when I downgrade my plan?
When you downgrade your plan, any custom field data synced on your previous plan will be retained, but going forward, only data available on your new plan will be synced.
If you intend to use this previously synced data on your new plan, be aware that it risks becoming out of date. Custom fields such as ‘Date of Last Order’ or ‘Tags’ may be misleading.
To ensure all data is 100% accurate, you may even want to delete and recreate your list in this case (all data available to the new plan will be resynced).