When we make a request:

[more formal] [less formal]I would be grateful if you could … . Could you possibly … ?I would appreciate (it) if you could … . Could you please … ?

 

When we agree to a request someone has made:

[more formal] [less formal]I would be delighted to … . I will be happy to … .(delighted means very happy)

 

When apologising:

[more formal] [less formal]I apologise for the delay in replying. Sorry for the delay in replying.I/We apologise for the inconvenience. Sorry for the inconvenience.I/We apologise for any inconvenience caused. Sorry for any trouble caused.Please accept our/my sincere apologies. I/We are very sorry … .

 

When giving bad news:

[more formal] [less formal]I/We regret that … . Unfortunately … .I/We regret to inform you that … . I am sorry to have to tell you that … .I am afraid that I must inform you of/that … . I am sorry to have to tell you that … .

 

When complaining:(The following phrases may be used as the opening line of the letter or email.)

[more formal] [less formal]I/We wish to draw your attention to … . I wanted to inform you about … .I am writing to complain about … . I would like to complain about … .

I am writing to express my dissatisfaction with … . [none]

 

(The following phrase may be used as the closing line of the letter or email.)

[more formal] [less formal]I would appreciate your immediate attention to the matter.

I would appreciate if you could sort it out as soon as possible.