付款条件的英文表达 — 国际贸易填空题

某出口公司与韩国客户成交一批运动背包，合同约定：买方须在收到卖方形式发票后7个工作日内，以电汇（T/T）方式支付合同金额的20%作为定金，其余80%货款于见提单副本后付款。请补全下列付款条款的英文表述（每空一词）：Payment shall be made by T/T. The buyer shall pay 20% of the contract value as a down payment within seven working days after receiving the seller's proforma invoice, and the balance of 80% shall be paid ____ presentation of the copy of the Bill of Lading.