“It's not personal. It's business.”

If you've just been promoted over people you used to work beside, you're going to need that line. Probably sooner than you think.

It usually starts small. Someone on your team keeps showing up late. Last month they were your coworker. Maybe your friend. Now you're running the shift.

The work backs up. Other people have to cover for them. You can feel everybody watching to see what you'll do about it. Part of you wants to do nothing.

The talk

Pull them aside. Performance talks don't happen in front of everybody. Tell them plainly what's coming, whether that's a write-up or a hard review.

Expect pushback. They'll probably play the buddy card and give you their reason. Let them say it, and tell them you get where they're coming from. Then say the line.

It's not personal. It's business.

They'll probably be upset. Your stomach will be in knots.

What happens after

People usually come around, even if it takes a while. The friendship can make it through, too.

Let it slide, and you'll be having a harder version of the same talk a month from now, with the whole team watching.

Say the hard thing plainly. Don't let people spin their wheels, struggle, or pull down the people working next to them.

How do you review someone who used to be your peer?

If you're a new manager looking at a review for a former coworker this month, here's what I'd tell you.

• Talk in private. Every time.
• Let them give their reason, and hear all of it before you answer.
• Talk about what it did to the team: the work that backed up and the coworkers who covered.
• Your friend gets the same rules as everybody else. The rest of your team is watching for that.
• It's going to feel awful. Have the talk anyway.

Why I still say it

Some people think “it's not personal, it's business” sounds cold. I don't. It keeps your head on the job when it would be easy to make it about the friendship, and I still say it to new managers today.

If you've got a review to write for someone you used to sit beside, don't sit on it. Just remember, it's not personal. It's business.