[gfolds]

Apart from the generic question of the pros and cons of using Excel as a data store and how you solve issues around access control, concurrent access, backups, etc., financial databases have some additional requirements to be properly auditable. For example, one of the biggest differences is that the data should be immutable with only additions allowed. E.g. if you made an error and need to correct it (say you sent the wrong amount of money to someone or simply just had a bug), you should keep the record of the erroneous transaction and reverse it or book an adjustment.

You can try to institute the same controls over Excel, either directly in code or just implicitly in terms of how it's used, but they tend to break down pretty quickly with scale.