Accounting for Transfer of Unit from Old to New Customer

Hi,

We have a requirement to transfer unit sold to one customer to another.

E.G

Unit Total Value: 500K

OLD CUSTOMER: Invoice was created for 100 K and received money from customer 100k.

Later OLD CUSTOMER cancel the lease agreement and now this unit was transferred to NEW CUSTOMER with the balance amount.

Now question is, do we need to reverse cash received from OLD CUSTOMER and transfer this money to NEW CUSTOMER.

What should be the accounting entries for transfer of units in OLD and NEW CUSTOMER ACCOUNTS.

Regards,