Invoices that have fields with background raster (patterns consisting of shades of gray) can cause problems with interpretation. If you encounter problems, try one of the following solutions:
You can ignore the problem and INVOICES' interpretation algorithms clean up the noise internally.
Try applying a background filter on the fields with background raster.
Try adjusting the noise removal. This can be tricky, because if this setting is low enough to ensure that all written information is preserved, undesirable raster points may also be preserved as black specks in the black and white image.