Hi, 

The finance part may be easier than the ops side.   From the ops side most things are connected to a site, the site can’t be moved from company to company. Need to create a new site.  That includes all the basic data - work centers, parts, routings, labor class, costing - etc. 

The finance side, the customers and suppliers would need to be reviewed and in some cases changed so the invoice / payment information is connected to the revised company.  For customers you would also need the credit information.

Then you have all the basic data including payment terms, banking  information, cash accounts, payment institutes etc.  

You would need to look at the code string related data, accounts, account groups, code part values, etc.  Assuming we followed a good process where all the company data was the same from company to company this may be a lesser concern. But if the basic data is different for example cost center values are different, then you need to merge all that basic data.   You need to review all basic data / especially data that was different from company to company. 

Then you need to determine how or if we need to keep that data separate. As two companies you had different data sets - ability to create financial reports by company.  After the merge- what are the requirements?   No longer have that need? Or do you still have the need?   That will need to be asked and resolved. 

Then you have the history - open AR invoices / open AP invoices - credit notes and all that data.  

This is a big process, and not something you can ask of the community (in my opinion). You should (in my opinion) seek assistance from an experienced consultant who has seen this a time or two. It will save you countless hours.

Best regards, 

Thomas