We are very sorry to inform you which is about L/C discrepancy. 想請問一下，這樣寫文法上是否有錯 我該用 which 嗎?

... inform you which is about...

1. 一般而言,關係代名詞(這裡的which)是在說明之前緊接的名詞(這裡的you). 所以你的寫法是錯誤的.

2. 你應該用<直接受詞>的用法:

We are sorry to inform you that there are a few discrepancies on the L/C.

在這裡,"that there are ... L/C" 是 inform 的直接受詞. "you"則是間接受詞.

3. 另一個問題是 sorry 的用法.他有定論的隱喻.除非你已經決定要拒絕這個LC,不然你應該避免.

We are very sorry to inform you which is about L/C discrepancy.
應簡化為
We are very sorry to inform you of the L/C discrepancy.

to inform you which is about=that there is discrepancy about L/C
=about L/C discrepancy.
In defining or restrictive clauses, often replaced by that; and used with no selective meaning,no pause,no set off;no need to do with the relative pronoun as the subject of the verbs "are to inform" No need with the relative pronoun as the object of the verb"to inform"
it is a superfluous,more than is needed or wanted;
Hence no need "which is"--an amount that is more than is needed.
eg:-We are very sorry to inform you about L/C discrepancy.