Finally, under Guideline 6, the AML Guidelines provides that art businesses must maintain adequate records of their due diligence efforts. Perhaps stating the obvious, but perhaps also implicitly acknowledging the existence of practices by certain dealers, the AML Guidelines observe that “[a]ll documents issued by an Art Business in connection with a transaction (e.g. valuations, sale and purchase agreements, invoices, shipping documents, import / export declarations etc.) should be true, accurate and contemporaneous and represent the honestly held professional opinions of the Art Business.” Likewise, dealers “should refuse all requests from clients to alter, back date, falsify or otherwise provide incomplete or misleading documentation or information relating to a transaction. If there are legitimate reasons for altering a document (e.g. invoicing error etc.) the circumstances and justification should be fully documented and retained on file for future reference and audit.”
The ownership history of a work of art is of fundamental importance for all those involved in the collecting, exhibiting and study of art, for determining both attribution as well as legal title. Recent ownership claims by heirs of Holocaust victims whose art works were looted or otherwise misappropriated during the Nazi-era, and also claims by foreign “source” countries for objects they believe were exported in violation of patrimony or export laws, underscore the importance of provenance research. 
The notion of intellectual property—the idea that artists’ works belong to them—dates at least to medieval Europe, though history records examples of the concept as early as ancient Greece. It had taken hold sufficiently during the Renaissance for Michelangelo to take umbrage when his work was misattributed. It was reported that when he discovered that another artist was receiving credit for sculpting the famous Pietà (now in St. Peter’s Basilica in Rome), Michelangelo returned with his chisel and added his signature across the centre of the sculpture, on the prominent sash across Mary’s upper body (in Italian): “Michelangelo Buonarroti, Florentine, made this.”