The MS learn articles below are clear that financial tags cannot be deleted, even if they've never been activated

• https://learn.microsoft.com/en-us/dynamics365/finance/general-ledger/financial-tag
• https://learn.microsoft.com/en-us/dynamics365/finance/general-ledger/fin-tag-custom

Given that the stated reason is to maintain data integrity, it feels feasible that a job/script be written that checks data integrity and then allows tags to be deleted if they've never been used.