Not having written proof will affect the outcome,but the fact that he is taken to court will have a big impact.
Such mistakes are done by many due to lack of experience and urgency to get a job,but then we have to find way out so that you do not loose your due entitlements.
Do you have details of work done?
Has he paid any incentive so far?
This will help prove that incentives were being paid and rate can also be worked out.
Pay was by cash/cheque??
Collate whatever documents you have,SMS,email etc.
Do consult a lawyer and set things right.
Let the employer not get away because he was smart enough not to leave documentary trail.
Yes He was paying me by cheque . and he had never given any incentives yet (he was like will pay you with salary next month )
And regarding details of work done, I used to work on leads given by him and , on every paper name was in the name of that consultancy only rather than any employees name , so unfortunately can't work out on that also .
But client for whom i was working , very well aware about my dedication and work done.
Definitely other employees would have received incentives.
This will prove that incentives are a part of your salary structure.
The client may be able to give indirect evidence of your work.
Consult a lawyer and see what can be done.
The affected employees must be rallied together into joining hands.
You were promised a remuneration which included incentive,now if they decline incentive,it is breach of contract(even if it is oral)
How your current employer will view it cannot be commented upon.
Some employers may agree with you but some may think -employee is litigation minded.
One has to take a call.Nothing can be won by indecision or hesitation.If you feel there is a need to "teach a lesson" as you earlier said,then file a case.
But know your weakness-oral commitments,no documents etc.