As P45s state. Total pay to date and total tax to date.
Tax is BR (20%) regardless for self employed on my slips anyway.
Granted there's several ways you can be contracted, but out of every company I've worked for, I've always received a P45 after each contract.
Well, that's very weird, as if you were a contractor, they shouldn't really be deducting tax from you. They're only obliged to deduct tax if you're employed. Perhaps there was some doubt over your employment status, as Ring Peace has inferred above.
I suppose there could be something in it if you fell within the Construction Industry Scheme, but I don't really know how that works, so I couldn't comment any further on that.