The AP workflow has a Lookup Vendor Datalink uses the company, site, and name to check for vendors.
Sometimes the invoices come into ECM with the wrong company (some vendors exist in multiple companies), and I thought this vendor validation step in the workflow would catch them.
When I check the Integrations section, I don’t see the company and site parameters. I’m not even sure how to test the Datalink to make sure it’s working.
Am I missing something?
The vendor name is the only thing in the lookup. In the post below I went over how I would approach this if I was multi company. Change the view in IDC to have pipes in the results and the use a split to get the company and vendor id, so the xml delivered to ECM already has that.
Yep - this is a typeahead “lookup” for a drop-down box. The value on Item#2 (@LOOKUP) is a string based on what the user would type into a box and then be “looked up” or matched to. For example, if I type “mcmas” in for @LOOKUP, my vendor search would return “McMaster-Carr” for the Vendor. It also uses the settings just above the Datalink, where the integration details are, for the Company Value. Which makes this difficult to test and control. We don’t use it.
As for your problem with vendors in multiple companies, I do something similar to @gpayne but I think it’s simpler. 
I have a view inside the IDC database, that ‘views’ data in the ERP database. It has the basic vendor details including company. Then, in the Batch Type definition, I have validations lists for each of my companies that includes a filter clause. Then I use those validation lists on my company specific DFDs. With all of this set up, the Data Verification phase validates vendors based on the right company and sends only valid data over to ECM.
This can be done any number of ways.
It looks like we do have a validation list in each of our batch types for the specific company. We were set up with a batch type per company, and then one document form definition (AP Invoice) that they share.
If each batch type or company has its own watch folder then your setup is like @MikeGross’s and should work fine.