1. Please excuse my late reply to your very friendly letter of March 1.
2. I hope you will forgive me for not having written you for so long.
3. I hope you will excuse me for not having replied to you until today.
4. I humbly apologize you for my delay in answering to your kind letter of May 5.
5. I have to (must) apologize you for not answering your letter in time.
6. I must ask you to kindly accept our excuses, late as they are.
Opening Phrases & Sentences Generally Used In Business Letters
1. I will write you particulars in my next.
2. Particulars will be related in the following.
3. I will relate further details in the following.
4. I will inform you more fully in my next.
5. I will go (enter) into further details in my next.
1. As stated below,
2. Annexed hereto,
3. Attached you will find...
4. As shown on the next page
5. As indicated overleaf(下页，背面)
6. As at foot hereof,
7. Sent with this,
8. As the drawings attached,
9. As shown in the enclosed documents,
10. As already mentioned,
11. As particularized on the attached sheet,
12. As detailed in the previous letter,