When mentioning time period, is it correct to use the phrase "now onwards"? can we use 'onwards' after 'now'? or should we use only 'now on'?
The idiomatic expression is "from now on". As this ngram shows, 'from now onwards' has been used very rarely in comparison.
We will do this from now on.
Other similar expressions include:
- We will do this in future.
- We will do this from now on.
There is also an expression "going forward" (eg "we will do this going forward") but this is disliked by many as it is considered a meaningless corporate buzzphrase.