Having to pay something for doing something is a negative incentive. Now, the activity has a cost and your will or need to do that activity will have to be superior to your will to avoid the cost of it. A negative incentive is the one that that require individuals to act in a certain way in order to avoid a loss.
Some positive incentives can be also presented as negative incentives.
If a company presents a bonus as part of the salary but says that the employee will lose that bonus if some performance requirements are not met.