一個月離職通知, 英文係點寫?

"One month notice period.." is commonly used.

Here is one of the example for your reference:-

Unless otherwise specified in your appointment letter, the notice period or payment in lieu of notice required to terminate the service by either the Company or an employee is as follows:

Length of Service Notice Period
============ ============
First month Not required
Second month till confirmation1 month
Thereafter 1 month or 3 months

One-month's leave notification

Yes.
You can also say "to give one month's notice of resignation" .

Hope that helps ^^

one month notice, 這句也可