Setup > Company > Subsidiaries > New > Save > This record already exists.

First, check the list of subsidiaries. If there is already a created subsidiary with the same name, users may want to alter the name to not match the other subsidiary.
If there is none and the user is still getting the error that the record already exists, it may be due to account name collision. Account names should be in this order:

[One Account Name]
[One Account Name] [1]
[One Account Name] [2]
[One Account Name] [3]
[One Account Name] [4]

There should be no gap in the order if the accounts are carrying the same name.

Below is a screenshot of the accounts in incorrect order.

Users will have two options:
1. Rename the accounts to follow the above order.
2. Change the prefix of the account name to something else (instead of "VAT Liability", "VAT on Purchase", or "VAT on Sales").

Note:
- This scenario may occur if a subsidiary was deleted and needs to be recreated.