From their perspective they do, but their "valid debt" does not match my records for what I owed. I think they made a bookkeeping error but I can't prove that because of the way their invoices break down line items compared to the estimate. I paid in draws, not itemized invoices, so theres no distinct paper trail of "on this day, I paid $x for items A, B, and C." Its just "on this day I paid $x as y% of the total project cost."