When a proforma is enough
A proforma is the estimate before the order is firm. The commercial invoice is what you send when you want the wire.
Use a proforma to get a yes
Send it when the client needs a figure for internal approval, or before the scope is fixed. It is not a demand for payment.
Switch when you want to be paid
The commercial invoice names the agreed work, the final amount, and the bank account. In Wire Invoice, that is the invoice, not the estimate. Turn the estimate into the invoice when the work is sold.
Do not ask them to wire a proforma
Some clients will, and then argue about the difference. If you want the money, send the commercial invoice.