How does a team get a negative dead cap? I see where a team is way over the cap and it's mainly because he has a dead cap of over -$30m?

I know of a glitch in early free agency that can create a negative dead cap number, keep in mind though that a negative dead cap number would help with your cap, not hurt it.

https://mfn71.myfootballnow.com/team/3

What creates this is getting to early free agency with less cap room than "Need for Draft Picks". For some reason on each cycle of early free agency it will match your "Room under cap" with "Need for Draft Picks" if your "Room under cap" is lower. It does this by subtracting the difference from your dead cap, actually lowering your dead cap penalty. In fact I've tested this before on multiple occasions and it makes dead cap completely irrelevant. I'm a little surprised that JBD still has not implemented a fix for this. It has been around as long as I can remember. It's so laughably broken that I never factored the dead cap in when trading guys with large salaries because I knew if I ran into cap issues I'd always have room for my draft picks and it would just be gone in a season or two anyway.

JDB: If true, why not a fix?

here is that team = https://mfn71.myfootballnow.com/team/22

that user has been playing for 2 months so maybe that has something to do with it.

This is a side product of code to protect the sim from crashing if a team is in such poor cap situation that they don't have enough cap room to field a complete team even with the minimum salary. It does probably need to be handled more elegantly.