Sir, I need a day off so, could you please grant me a leave for coming Monday?

[tufguy]

1) Sir, I need a day off so, could you please grant me a leave for coming Monday?

2) Sir, I need a day off so, could you please grant me a leave for 12/05/2018?

3) Sir, I need a day off so, can I get a leave on coming Monday?

4) Sir, I need a day off so, can I get a leave on 12/05/2018?

Please check my sentences.

 

[bubbha]

The comma should be placed before "so", not after it.

"leave" is an uncountable noun.

The word "the" should be placed before "coming Monday".

 

[tzfujimino]

... or maybe 'this'.

"... this coming Monday ..."

(Edit)
I'd like to suggest that you follow Rover's advice here:
https://www.usingenglish.com/forum/...-on-10-01-18-so-all-the?p=1454038#post1454038

 

[Tdol]

How about:

Could you give me a day off this coming Monday?

 

[GoesStation]

How about:

Could you give me a day off this coming Monday?

Tufguy, note that asking for a day off tells your boss that you need one. You don't have to state that bit. ;-)

 

[tufguy]

Tufguy, note that asking for a day off tells your boss that you need one. You don't have to state that bit. ;-)

Is it correct to use "on" or "for" before the name of a day or a date?

 

[GoesStation]

Is it correct to use "on" or "for" before the name of a day or a date?

Both are possible. Which one is right depends on the context. Maybe you should post this question, with a sample sentence, in a new thread.