供應方通常會連同貨物寄上發票（invoice）或形式發票（pro-forma），用意是向買方說明：
1. 交付的貨物（the goods delivered）；
2. 應付的款項（the amount due），即使是以「試用」或「寄售」方式發送的貨物（good sent ‘on approval’ or ‘on consignment’）；
3. 方便買方在購貨簿（purchase day book）記帳；
4. 有時需要說明貨物的價值（value of goods）作報關用途（for customs purposes）。
5. 發票通常連同貨物寄發（sent with goods），那就不需要加封面函（covering letter），如果發票是先於貨物獨立寄出的，就需要加封面函了。
6. 最後，發票上的 E & OE指errors and omissions excepted（如有錯漏，可予更改），即供貨方補留修改錯漏的權利。
寫發票封面函的有用句子
l We are pleased to enclose our invoice number ________ for the [name of goods] ordered on [date].
l Our invoice number ________ is enclosed covering [name of goods] ordered on [date].
l The goods are available from stock and will be sent to you immediately when we receive the amount due, namely US$________. （對新客才會這樣寫，意即必須先付款才發貨。）
l The goods have been packed ready for dispatch and are being sent to you, carriage paid（運費已由我方支付）, by air. I think they should reach you by Tuesday.
若你少計了對方100元，要在對方帳戶扣回100元，這當然要通知對方，這種「我在你帳戶扣了款」的通知叫Debit Note（借記通知書）。
寫Debit Note的有用句子
l We
deeply regret that… We have enclose a debit note/a refund cheque for
$_____, which covers the replacement amount plus your shipping cost for
returning the order.
l We regret to have to inform you that an unfortunate error has been discovered in our invoice number [AB5354] of [date]. The correct unit price for the 10,000 pieces of [name of goods] should be $166 and not $160 as stated. We are, therefore, enclosing a debit note for the amount undercharged, namely ($166-$160) x 10,000 = $60,000.
l The
mistake was due to a typo/a typing error/a clerical mistake, and we are
sorry it was not noticed before the invoice was sent.
如買方發覺賣方多收了錢，買方可以在賣方的帳戶扣除該款，然後向賣方發出Debit Note，並要求賣方發出款額相同的Credit Note（貸記通知書）以作確認。這要求叫Request for a Credit Note。賣方「credit」了買方的帳戶，就會向買方發出credit note，即通知買方：「我已在你帳戶記入了一筆錢」）。
要求對方發Credit Note的有用句子
l （要求Credit Note） We have today returned to you by ship 1,000 empty packing cases, charged on your invoice number [AB5354] of [date] at $________. A debit note for this amount is enclosed and we shall be glad to receive your credit note in return.
l （要求Credit Note） Your invoice number ________ of [date] allows a trade discount of only 25% instead of the 30% to which you agreed in your letter of [date] because of the usually large order. Calculated
on the invoice gross total of $100,000, the difference in discount is
exactly $5,000 and if you will kindly adjust your charge we shall be
glad to pass the invoice for immediate payment.
l After receiving the goods you sent to us on [date], we found several defects, namely _______________. To meet our customers’ urgent demand, we have already corrected such defects at a cost of US$1,000. We will accordingly deduct the same amount from the invoice you submitted to us on [date]. Please refer to the debit note attached and sent us a credit note for confirmation.
拒絶發credit note的有用句子
l Unfortunately, we cannot issue a debit note for $_____, as it is an additional expense you incurred in the course.We received your letter of [date], but we have no trace （找不到）of the returned goods. It would help if you could describe the kind of container in which it was packed （請問用甚麽裝的？） and state exactly how it was addressed（地址是怎寫的？）. As soon as we receive this information we will make a thorough investigation. （意指未查就不會credit你的account了，所以說以下的話）Meanwhile, I am sure you will understand that we cannot either provide a free replacement or grant the credit you request.
