I'm a sole proprietor and I partnered with an actual S Corp company on a project. I paid them their share.

When I file my taxes in April and need to deduct the amount I paid the S corp (so I don't get taxed on it), do I need to show proof of the amount I paid them (check images)? Or does the IRS take your word for it and in case of audit, then you show proof?

How does it work?

Thanks