催款函是卖放在规定期限内未收到货款，提醒或催促买方付款的函件。
写此类催款函要求文字简练、意思清楚；同时要求语气诚恳、体贴，彬彬有理。不可轻易怀疑对方故意拖欠不付，以免伤害对方感情，不利于达到索款的目的，或妨碍以后的业务。对于某些屡催不付，故意逃款的客户，语气则要强硬，措辞坚决。总之索款要把握一个原则：既要达到索款目的，又要与客户保持友好关系。
外贸英语函电：催款函范文实用范例
（1）subject demanding overdue payment
dear sirs,
ac no.8756
as you are usually very prompt in settling your acs, we wonder whether there is any special reason why we have not received payment of the above ac, already a month overdue.
we think you may not have received the statement of ac we sent you on 30th august showing the balance of us$ 80,000 you owe. we send you a copy and hope it may have your early attention.
yours faithfully,
xxx
催款函主题：索取逾期账款
亲爱的先生：
第8756号账单
鉴于贵方总是及时结清项目，而此次逾期一个月仍未收到贵方上述账目的欠款，我们想知道是否有何特殊原因。
我们猜想贵方可能未及时收到我们8月30日发出的80，000美元欠款的账单。现寄出一份，并希望贵方及早处理。
你真诚的xxx
（2）subject urging payment
dear sirs,
ac no.8756
not having received any reply to our e-mail of september 8 requesting settlement of the above ac, we are writing again to remind you that the amount still owing is us$ 80,000. no doubt there is some special reason for delay in payment and we should welcome an explanation and also your remittance,
