Non-PRO English to Russian Law/Patents Law: Contract(s)

With reference to the last term of payment, CONTRACTOR shall submit to Y a bank guarantee for warranty period in form and manner as attached hereto in Appendix x and in the amount of xx% of the final amount, before CONTRACTOR shall submit its invoice for the balance of the final amount.

Непонятно окончание фразы.

Может, всего-навсего, исполнитель направляет счет-фактуру для выплаты конечного платежа?