I.R.I.S. Readiris 14 for Windows User Guide - Manual (Page 151)

How to
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H
OW TO RECOGNIZE FORMS
Note that Readiris is not designed to recognize complex forms.
Readiris recognizes documents by converting pictures of text
characters and numbers into actual text and numbers. Forms, on the
other hand, contain many graphic elements such lines, boxes, check
boxes and the like, which complicate Readiris tasks.
Use the following rule of thumb if you try to recognize forms: if
you would be able to re-create the form fairly easily from scratch
inside Microsoft Word, Readiris has a good chance of processing it.
If it would take an extraordinary effort to re-create it in Word, then
Readiris will have the same difficulty.
Example
Form Readiris would not be able to process correctly