There are five performance levels you can group your reports under:

1) close to promotion, performing at the next level + at their level
2) trending back from near promotion to more at the current level
3) at the current level
4) trending from the current level to under-performing
5) consistently under-performing

When a person is performing in bucket #1, you gotta be very sure they are performing at their level and the next one consistently. They must have long-term potential (in part they show this by temporarily operating at two different levels) and be moving to the next level consistently (slightly above #4 for the next level only trending upwards/forwards instead of backwards/downwards). And if they are, it is your responsibility to get them promoted.

For #2, the employee is trending back from close to promotion back to performing at the level. This can be very hard for an employee to hear, but you have to give feedback if this is the case. You have to let them know that they are trending back to #3. And you need to be specific and concrete about why (i.e., include at least two anecdotes and ideally some measurable data). Finally you should setup a plan for how to close the gaps to get back to #1. Great managers do this proactively.

At #3, you have to tell them why they are not yet performing at the next level and what they are doing at their current level that they can do better to get to #1. Again specific examples are essential for constructive feedback. And charting the path to get to #1 is one of your most important (and hopefully enjoyable) things to do as a manager.

At #4, you need to start coaching them consistently. You absolutely have to (an inexperienced manager will make the mistake of not being proactive about this bucket). You need to meet weekly or regularly and work towards specific goals. You can't sugar-coat
it, you have to be real about whether they are on track for these goals; and if not, and circumstances are outside of their control, you need to find other ways for them to demonstrate moving back into #3. Your skip manager and potential HR business partner need to start becoming involved. You do your employee a disservice, while in this coaching period, if you mislead them into thinking they're at #3 when they're still in #4. Set super clear goals and be crisp about the gaps that need to be addressed to get back to #3. It is super important when a colleague enters #4 that they know what is at stake. The goals set out in #4 have to be finished in the coaching period you outlined then. If they are not, they will move to bucket #5.

If they are in #5, by definition they need to have already been given consistent coaching. (Note if an employee does something fragrant, they jump to #6, i.e., discussion with your management and HR business partner about immediate termination. These buckets are for non-fragrant cases.) So being in #5 by definition means they've had consistent coaching but they have not been able to close the gaps. It's related to work, it's not personal, but within #5, depending on your company's policy they should probably have alternatives for leaving the company here. E.g., some sort of severance option or a performance improvement plan with very strict goals where it is
abundantly clear that since they have not met the role guidelines for the role and level, and despite the coaching which should take on from 1-2 months, their performance has not improved. Within bucket #5 if they do not perform against the performance improvement plan, they will be essentially managed out.

I don't know how it works at more senior levels -- if people are expected to just be at #3, #2 or #1 and so there's no real #4. I'm not a senior manager or director. Maybe it gets accelerated. Perhaps #3 and #4 combined and so feedback is essential but there's not the luxury for taking a few months to coach. Perhaps all levels of management should follow these five buckets. I don't know.

But I do think if you're in #2, #3, #4, #5 which statistically probably 85% of people -- to improve you need to listen keenly at every hint your manager gives regarding feedback.