Thanks all for the added comments!

In this particular case they may have justification in the contract for what they are demanding. I don’t know. If they do have justification, I have no problem paying what they are demanding, nor do I have a problem meeting their deadline. But I don’t think it is unreasonable for them to provide proof of their assertion. So far they are unwilling to do so. I just don’t want to get a whack on my credit rating due to their refusal to comply with my request. And I don’t know if they are obligated to comply with my request.