Need to replace rear middle seatbelt

You can check for a replacement at the dealer if you want a new one. I'd guess it'll be pretty pricey from them. You could find one from a junk yard or car-part.com. You do risk rust/corrosion/etc this way though, and a seat belt isn't something that you want to break in a time of need because someone's life could depend on it. It's not too complicated to replace if you're handy with a wrench. A single (large) bolt holds the assembly in place.

Thanks! Just to clarify, the rear middle seatbelt connects to the inside roof - how easily does that panel come off? The dealer priced the seatbelt at $300 + installation!

I've heard some Subaru dealers take safety so seriously that they will replace the belt for free. What caused the tear in the belt?

^ That's a good point to bring up. I think it's federal law that all seat belts have a lifetime warranty on manufacturer defect or wearing out. That doesn't include unusual abuse or user error tho.