When John is handing his Dad a beer at the shanty we see his hand reach into the bag and pull out a beer. In the next shot we see his hand back inside the bag and hear it dislodge the beer from its holder.
John reaches into the back seat of his car to retrieve a tax folder. Jacob approaches and greets John. When John turns around to return the greeting his hands are empty. In the next shot he once again has the folder.
The IRS at the time of the movie didn't audit a year if it was over ten years old. In the movie they said he collected for 20 years and eleven of those 20 were not claimed properly. That is past the ten year mark. He had not been collected for probably a number of years so, those years would not have been audited and they wouldn't be entitled to anything.