Q. "Can we cut a performance improvement plan short if the employee's performance has gotten worse?"
Answer:
In general, yes. When an employee is on a performance improvement plan (PIP) and their performance has not improved but gotten worse, it is perfectly reasonable to cut the timeframe short and move forward with further disciplinary action, including termination. Unless it’s written to say otherwise—and it shouldn’t—a PIP is not a guarantee of employment for the duration of the plan. It shouldn’t alter the at-will employment relationship.
Be sure you are following historical practices if you have had similar situations in the past. The most important thing is to remain consistent. Document and tell the employee why the PIP was cut short listing each policy violation or performance issue individually in case you are asked to provide context later.