using De Minimis election for tangible property what are the invoice requirements

I want to elect the de minimis for various expenses related to equipment and production of youtube content and ebay.  I have turned a profit and wanted to make use of the de minimis election.  I am a sole proprietor.  My main concern is the "invoice" requirement.  I have receipts for all purchases, and invoices from various locations.  Is that all I need, or do I need to actually have a separate invoice made? 

 

Thank you for your help