Are you using a modified form created in a version of Sage 100 before the multi-SO invoicing feature was added?  If so, that is the problem.  The new invoice forms have extra features to handle the multi-SO feature, and old forms are not automatically updated for things like that.

You'll have to look into the form using Crystal Reports.  Be sure to test all changes / customizations (like adding fields / UDFs).

I am sure we are because we haven't updated the forms since we started to batch invoice.  Might seem like a stupid question but how do you update the form for the new features?  Learning on the fly but I do have a test company to play around in, rather not go to our SAGE consultant and gain the knowledge on my own.

Go into your test company, SO Invoice printing, type in "TEST" as the form code name, then click Designer (only there after your workstation has CR installed and you have the Role permission to use Designer).  This should copy in the default Sage invoice form template for the version you are running, to safely modify without affecting anything else.  Starting from this and adding what you want will be much easier than upgrading your old forms with the new structures needed for multi-SO invoicing.  Once you have the working report, it can be copied for use Live.

Add the fields you want into the form's work table as UDFs (instead of linking tables).

If you are not already familiar with Crystal Reports, you're going to want some help.  I've been designing reports with CR for over 20 years, and significant customizations can take ME hours to do.  Trying to teach yourself as you are going along will be more costly than paying for training.  Even then, almost every time I've given Crystal Reports training to one of our customers, they have not used it enough to retain the ability to make more than superficial changes to a report, and they still end up coming to us for everything.

I am looking into this again and noticed the new invoices forms have the "applied so" and "appliedcustomer po" fields availibale to print on the invoice.  Is there ways to add other fields from the header in this "applied" structure without adding an UDF?  The "CONFIRM TO" field in the So header is another field we need to print on the invoice when batching them.  And I am assuming I am understanding the "applied" fields correctly.