Proof of Purchase questions the medium of receipt paper as a form of monoprint. I unearthed deeper meaning rooted in these ephemeral objects and images by heating, soaking, and folding receipts I had collected. Notions of memory, nostalgia, place, and identity permeated these altered spaces. As a community initiative, I asked others to share their receipts. Together we created a series of obfuscatory collective memories punctuated by monetary exchange. Proof of Purchase unveiled the intertwined economic and social forces scaffolding individual lives. This series expands the genre of monoprints to include modes of thermal, chemical, and mechanical alteration; potential works of art in the hands of millions of people across the world.