most common paper money errors are: -design and engraving errors -printing errors: incomplete printing, offset printing, double printing, out of registry printing, misplace print, misplace, offset image or lack of signature or date, ink smears, inverted back. -numbering errors: mismatched prefix letters or serial numbers, partial digit serial number, missing number, misplace serial number, duplicate serial number -cutting and folding errors: folds before printing, folds before cutting, cut out of registry, cut of size. -overprint errors: double print, inverted print etc.