next month
fixed phr..fixed phr.. This phrase refers to the month that will come after the current one.
fixed phr.. An adverbial phrase of time indicating the calendar month immediately following the present one.
Her new job starts next month.
We are going on vacation next month, so I need to book the tickets soon.
The fiscal report, which will be published next month, is expected to influence the central bank's policy decisions.
This phrase acts as an adverb, so you don't need a preposition like 'in' or 'on' before it.
Contrast 'next month' (the calendar month after this one) with 'in a month' (a period of time starting from now), as they can refer to different dates.
I will visit you on next month.I will visit you next month.When using 'next' with a time period like 'month' or 'week', you do not need a preposition like 'in' or 'on'.