I read a few comments back that it is better to come to a verbal agreement on a waiver instead of requesting it in a written document, is this agreeable to everyone?

My situation is as such:
1. Already have a different employer waiting to hire me, wants me ASAP as usual but not willing to pay out.
2. I am willing to pay out 2 months salary in lieu of notice.
3. I also need to pay the remaining months which I have not served since I am on contract. However I see that there is a possibility for it to be waived but it does not state how I can qualify for it.
4. I have only been in the company for 3 months and I do not have anything to hand over, and I would like to think that I am on amicable terms with my manager. I would like to keep these terms after resigning as well.