YOU SAID:

But I want to inform you, it took many months to process this bill

INTO JAPANESE

しかし、お知らせしたいのですが、この請求書を処理するのに何ヶ月もかかりました

BACK INTO ENGLISH

However, I would like to inform you that it has taken months to process this invoice.

INTO JAPANESE

ただし、この請求書の処理に数か月かかっていることをお知らせいたします。

BACK INTO ENGLISH

However, we would like to inform you that this invoice has taken several months to process.

INTO JAPANESE

ただし、この請求書の処理に数か月かかっていることをお知らせいたします。

BACK INTO ENGLISH

However, we would like to inform you that this invoice has taken several months to process.