一般來說對於契約的小修改，沒有必要重新簽訂契約，重新簽訂都是費時費力，也沒有必要，所以都用補充協定對原契約進行修改。如果對契約改變重大的話，比如對方想換個姊妹公司來簽契約，或者契約條款有多處重大變更，可以說從根本上改變了契約的內容，都可以重新簽訂契約的。重新簽訂契約有兩種方式。一種是交出所有原契約的原件，然後廢除，撕毀都可以，然後再簽訂新契約；如果對契約原件到底有多少份不清楚的話，保險起見可以先起草一個對原契約的終止協定，然後再簽新契約。當然如果為了做到天衣無縫，兩個契約之間權責無縫轉移的話，我自己使用過這種模式，不用撕毀原契約或者起草終止協定，先在新契約中寫終止原契約，一般寫新契約生效後原契約立即終止，在新契約未生效前原契約保持有效。然後在新契約上蓋上三種章，第一種是原契約的對方的章，第二種是新契約的對方的章，第三種是我方的章，這樣操作有個缺點是財務看見契約上有三個章，如果她們不看契約內容的話，有時候容易混淆契約內容。
言歸正傳，給大家分享一個我起草的比較簡單的補充協定。
忘了給大家說了，之前跟一位做國際工程的朋友討論補充協定和變更怎么翻譯，我傾向於契約變更翻譯為amendment, 補充協定翻譯為addendum.不知道大家什麽意見？不過我自己一般都是不加區分的用amendment的。
EXPLOSIVES SALE AGREEMENT
Amendment to the Contract Agreement
Between
The XXX COMPANY
and
MULTI BIZ FZE
WHEREAS: The Explosives Sale Agreement with Contract No: XXX for the construction of XYZ Motorway Road Project has been signed on 11 March 20xx between XXX Company(hereinafter called "the Buyer") and the MULTI BIZ FZE(hereinafter called "the Seller").
評註:先說我們什麼什麼時候簽訂了一個契約。
WHEREAS: The Buyer and the Seller have a meeting about the L/C and the Contract Agreement in the afternoon of 25 March 20xx, the Seller suggested that the volume of the goods is excessive and deliver them in one time would be hard; the Seller further suggested that the transshipment would not affect the goods quality since the goods are loaded with containers in the whole shipping period, it is very normal for cargoes to be transshipped in international shipment.
評註：再說這個契約要修改，為什麼原因修改，也可以把談判的過程加上。
IT IS HEREBY AGREED as follows:
評註：雙方都同意如下。
In order to ensure the smooth execution of the said Contract Agreement, it is agreed that the goods should be allow to transshipped and partial shipped; accordingly, delete the word "not" from second line, first paragraph of Clause 14 shipment of the Contract agreement (Contract No. CCCAAA-MBIZ-01-20xx).
The Seller further agreed that the goods would all be delivered within two shipments.
評註：上面就是要修改的內容了。
For any discrepancy between this amendment and any of the Contract Agreement, both parties agreed that this amendment to the Contract Agreement shall prevail.
評註：如果這個補充協定和之前簽訂的契約有衝突，那么以這個補充協定為準，一般可以不寫這一句，因為法律上規定一般是後面的檔案有效，不過為了避免爭議，也為了保險起見，我個人喜歡加上這一句。
IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be executed the day and year first before written.
On behalf of the Seller
Position___________________________
Name____________________________
Signature__________________________
Date____________________________
Tel____________________________
On behalf of the Buyer
Position___________________________
Name____________________________
Signature__________________________
Date____________________________
Tel____________________________
Witnesses
Name____________________________
Signature____________________________