1. A document bundler for a bill validator, the document bundler comprising: a document path comprising a wall; a transportation unit adapted to move a plurality of documents in series along the wall of the document path; and a clamp mechanism comprising a pushing member, the clamp mechanism adapted to clamp a first document of the plurality of documents with the pushing member to inhibit movement of the first document by the transportation unit while a second document of the plurality of documents is transported substantially alongside the first document in the document path, the second document residing substantially alongside the first document forming a document bundle, wherein the clamp mechanism is adapted to clamp the first document between the pushing member and the wall of the document path.
3. The document bundler of claim 1 , wherein the transportation unit comprises a drive wheel and a pinch wheel configured to push documents against the drive wheel, wherein the drive wheel slips on the first document when movement of the first document is inhibited by the clamp mechanism.