商务信函的书写规则（一）写信的原则（Writing Principles）已从原来的3（Conciseness, Clearness, Courtesy）发展到目前的７个"Ｃ"：Completeness, Clearness, Concreteness, Conciseness, Correctness, Courtesy,Consideration)实例Dear Sirs,Copper WireWith reference to your letter of April 9, we are pleased to accept your offer of 100 tons of Copper Wire as per your Offer Sheet No.8/070/02B. Please go ahead and apply for your Export Licence. As soon as we are informed of the number of the Export Licence we will open the L/C by cable.(信的本文汉译)：关于你们四月九日涵，我们高兴地接受你们第８／０７０／０２Ｂ号报盘单所报１００吨紫色铜丝。
请着手办理申请出口许可证。
的一经接到出口许可证号码的通知，当即电开信用证。
要求书信的"完整"，的理由有三：１．一封完整的书信比一封不完整的书信，有更大的可能性带来预期的效果；２．一封完整的书信，有助于建立和表达友善关系；３．一封完整的书信，可以避免由于遗漏重要情况（情报）所导致的诉讼（Lawsuit）；４．有时，某些不显眼的书信或文件，由于所提供的情况完整而又生动有力（Complete and Effective）而成为极为重要的文件。
一封信写得是否完整，建议用五个"Ｗ"来检验，既："Who, What, Where, When 及Why(包括How)"例如:在定货的信中，必须明确说明"需要什么商品"(What you want) "何时需要" (When you need the goods) "货物发到何地何人收"(to Whom and Where the goods to be sent) "如何付款"(How payment will be mande) 如对对方的要求作出否定的答复时（如不能报盘，不能理赔等）应说明理由"为什么"(Why)Clearness(清楚)（一）．避免使用可能产生不同理解或意义不明确的词汇〈例一〉As to the steamers sailing from Hongkong to San Francisco, we have bimonthly direct services. (从香港到旧金山有直达船，) 但是bimonthly 究竟是一个月两次即半月一次呢，还是两个月一次？不明确。
因此，最好清楚明白地说明"一个月两次"还是"两个月一次"：（a）We have two direct sailings every month from Hongkong to San Francisco. （每月两次直达船）（b）We have semimonthly direct sailing from Hongkong to San Francisco. （每半月一次直达船）（c）We have a direct sailing from Hongkong to San Francisco every two month. （每两个月一次直达船）（二）注意修饰词的位置，有时修饰词的位置不同，会导致不同的含意如：a) Please let us know what you wish us to do about this matter as soon as possible; b) Please let us know as soon as possible what you wish us to do about this matter. 以上两句中的""修饰的内容不同：a) 你们要求我们尽快做些什么。
b) 请尽快告诉我们。
所以a) 可译成"请告你们要我们为此尽快做些什么"；b) 可译为"请尽快告知，你们要我们为此事做些什么"。
（三）注意代名词，关系代词和先行词的关系按照英语习惯，句子中的代名词和关系代词一般是指离得最近的名词，因此要特别注意，以免引起误解或不清楚。
例句：不好：They informed Messrs.John & Smith that they would receive an answer in a few days. 较好：They informed Messrs. John & Smith that latter would receive an answer in a few days.(四)注意前后一致和紧凑，连贯不一致：Being a certified public accountant, I am sure you can help us. 一致：Being a certified public accountant, you can surely help us. or; As you are a certified public accountant, I am sure you can help us.商务信函的书写规则（三）Correctness（正确）商业书信必须写得正确，因为它涉及到买卖双方的权利，义务，厉害关系，是各种商业单据（如合同）的根据。
广义的说，商业书信的正确性表现在：（一）运用正确的语言水平（二）叙述得正确（三）数字要正确（四）正确理解和运用商业术语（五）合适的写作技巧或方法，以及正确运用其他的六个"Ｃ"。
一．正确的语言水平（１）正式的和非正式的语言水平所用词汇比较：的formal informalterminate domicile deem transpire conflagration edifice endeavor obtain; procure peruse remunerate utilize subsequent ascertain contingent upon anticipate interrogate end home think(or: believe) happen fire building try get read or study pay use next or following find out depending on expect ask （２）正式的和非正式的语言比较formal informal Will attain the age of 18 years. Will be 18 years old Render us more detail We will institute a mail search Send us more information We will ask the post office to send out a tracer. We thank you in anticipation of this courtesy and assure you that it will be a pleasure to serve you in a similar manner We shall appreciate your helping us. Let us know when we can return the favor. Inform me of your intentions as to the liquidation of this balance Let me know when you can settle this account. Give consideration to a plan. Consider a plan This plan will effect a saving of $10,000. This plan will save $10,000. To effect certain modifications in a procedure contingent upon the concurrence of management To make certain changes if management agrees. The conclusions ascertaind from a perusal of the pertinent data is that a lucrative market exists for the product in this vicinity. The data studied show that the product is in good demand in this area. （３）避免使用不标准的语言水平不要说的应该说ain't hadn't ought irregardless nohow in regard to can't hardly between you and I where ….at isn't, aren't shoudn't regardless anyway regarding can hardly between you and me where 下列是用一内容三种不同语言水平的比较参考：Formal: Although Item 12 is enumerated in the report, the writer has ascertained that it is currently not in the organization's inventory or in the writer's possession. Informal: Although Item 12 is listed in the report, it's not in our stock now and I don't have it either. Standard: Irregardless of the report that item ain't on our shelves now, and I haven't got it either.二．叙述得正确商业书信的内容要叙述得正确，既不要说得不够(Understatement)，更不要说得过头(Overstatement)。