When is your period considered late?// edit

I was supposed to start my period on Monday (5 days ago) and it has yet to show up and today would be my last day of my period. I’ve been seeing everywhere to test a week after your late/ missed So when you that be? Next Monday? Or next Friday?

Edit: I took a pregnancy test 2 days ago and it was negative. My period has never been late before. I’m just wondering if maybe I took it to early?