Due to private reason, I don't need to tell you more.

[output]

Is the following sentence correct and natural?

Due to private reason, I don't need to tell you more.

 

[Barque]

It isn't natural. It'd help if you explained what you mean by "private reason".

You probably mean:
I don't need to tell you more as it's a personal matter.
I don't want to tell you anything more, for personal reasons.

 

[Tdol]

You could use privacy concerns instead of private reason.

 

[emsr2d2]

It strikes me you're probably using more words than necessary. This could only be part of a dialogue. I imagine it would go something like this:

A: Tell me more.
B: No. It's private.