19.5Source-of-truth matrix

For important fields, create another small table:

Data	Source of truth	Can Salesforce edit?	Sync direction
Customer legal name	ERP	Maybe	ERP → SF
Phone	Salesforce?	Yes	SF → ERP?
Customer ID	ERP	No	ERP → SF
Account status	Billing	No	Billing → SF

This may reveal that the integration isn't actually:

Source → Salesforce

It may be:

ERP ───────→ Salesforce
Salesforce ─→ ERP
Billing ────→ Salesforce

Now conflict rules become critical.