Please note: This issue has been resolved in the HandiTax 2021, V3.03 update.
When rolling over a client from HandiTax 2020 to HandiTax 2021, an issue may occur where the related ref of that client is now attached to all clients that didn't previously have a related ref.
Please raise a new support case online, reference the title of this article and provide details of the issue.
NOTE: if using the SQL version of the software, refer to the following knowledge article: Access HandiSoft (SQL): Why do all clients have the same Related Ref?
To avoid this issue occurring again, remove the related ref from the client before rolling over. Once rolled over, you can add the related ref back to the client.