Hi Abbas,
Migration Strategy varies from one System to another depending on the Contractual\Statutory requirements, as till what time will the System will hold the data, so that customer can go and enquire about the same.
As per the Industry best practice, the following scenarios are considered for migration-
- Unallocated Legacy Payments
- Unallocated Legacy Misc. adjustments (Both Dr./Cr)
- Open Legacy overdue Invoices
Now in your scenario, I think, you have to migrate the cleared items in legacy system as well since Dec'13 apart from the above points.
In your scenario, what you can do is migrate everything from Dec'13 as Open Debit and Open Credit Items and not as cleared items. You can have a separate Mains for Legacy Invoice, Legacy Adjustments and Legacy payments, like CINV, CADJ,CPAY etc.
Once the migration is done, perform an account maintenance run in SAP, which will clear the settle the Open Debit and Credit Items based on the oldest due date and then only the latest Open invoices/Adjustments/Payments will remain outstanding against the account.
Hope it helps.
Thanks,
Amlan