A：We wish to change the SLA and include a provision for an agency representative to review all your works before it is sent for uploading on our website.
B：I don’t like the idea of having one of your representatives reviewing our work before we sent it for uploading. Why do you request this?
A：It is so that we know that the quality of the work is up to the standards that we want and expect. After all we are paying you quite a bit of money. Is this going to be a problem?
对话中的第三段A的回答中的it is后面是省略了吗？
It is so that we know that the quality of the work is up to the standards that we want and expect.
这句话不缺成分，什么也没省略。It is 后面是 so that 引导的从句作表语。即：so that we know that the quality of the work is up to the standards that we want and expect 是 is 的“表语从句”。
句子意思：如此（做），大家就会了解工作水平达到了大家想要和期望的规范。
下面是我以前的一个解答，看看这个剖析，就了解什么问题了。
The whole idea of going was so that we could meet her new boyfriend.
句意：去的全部目的是，让大家能见到她的新男友。
【剖析】so that we could meet her new boyfriend，在本句是表语从句。idea 在本句的意思是“目的”，不要翻译成“想法”。
so that 原本引导目的状语从句，目前可以用来作表语从句，但主语多为表示“目的”的词汇，比如：aim, purpose, idea, reason 等。
The reason why you add salt is so that it tastes better. 你在水中加入盐是什么原因仅仅由于味道好一些。
当然，主语也可以用代词充当，指代前面讲的某件事情。比如：
This is so that you can learn diving skills and how to use your equipment properly.
如此做，是要叫你们学习潜水的方法与正确用装备。
【说明】so that 的这种使用方法跟 because 类似，because 除去引导缘由状语从句外，还可以作表语。比如： Your failure is because you have not worked hard.