The most common and polite way to tell someone they are late is to use a respectful and understanding tone. Here are a few examples of how you can communicate this message:
"Hey, I just wanted to check if everything is okay. You're running a little late, and I want to make sure everything is fine."
"I hope there's no problem, but we were expecting you a little earlier. Is everything alright?"
"I know things can get busy, but we've been waiting for a while. Is there an ETA on when you'll be here?"
"I understand that delays happen. Just wanted to let you know we're here and looking forward to seeing you whenever you can make it."
"No rush, but we were hoping to start soon. Let us know when you're close."
The key is to express concern without being confrontational and to give the person the benefit of the doubt. Sometimes, unforeseen circumstances can cause lateness, and it's essential to be understanding and compassionate while addressing the issue.