If a contractor is working on a time/material basis with a markup or fee; then yes he has an obligation to furnish the underlying receipts and sub invoices. If the contract is being completed on a set price, then no, he has no obligation to furnish underlying receipts/invoices.
He does not have an obligation to provide copies of his bids, no matter the contract.
Its nice to be able to have a transparent contractor with great Integrity (ethics & morals) & that is how we are at www.AUORKC.com. Our business structure is as a cost plus construction & remodeling company. We have a fixed margin & so we are set up to share all receipts & invoices & we work on our own working capital & credit with suppliers & our team of trades. Its just like a Credit Card. We send out draws in arrears. We are a Volume driven & based company. Over the past 24 years, We have been able to grow a great business & we do a ton of volume.
Now a contractor would not show the receipts for trade subs or materials if its a bid. A bid is a sealed BID & you take the total amount & nothing more or nothing less.. if the contractor is doing a BID then they are not entitled to anything more if they under priced the work but BID items are theoretically over inflated so the contractor is covering themselves of all unknowns.