In Sage CRM, we have Match Rules defined for Company to restrict users from entering duplicate company records. Basically it is defined on Company Name field. Please refer below screenshot.
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Suppose we want to add another field for e.g. “Company Registration” for Company dedupe then we can follow below steps.
1. Go to Administration || Customization || Company || Screens.
2. Click on hyperlink of “Company Dedupe Search Screen”.
3. Add the “Company Registration” field and save.

4. Then go to Administration || Data Management || Match Rules || New.
5. You can see that “Company Registration” field is available in the Match Field dropdown as shown below.

6. Select the Match Type whichever you want and save.
After following above steps when you try to enter the company record with company name and Registration name which already exists in CRM then it will give you warning as Company already exists as shown below.

Also Read:
1) Enable De-duplication check in Act CRM
2) Data Upload using Deduplication
3) Change the standard dedupe behavior
4) 3 Easy Steps to Add Sage CRM Custom Entity in Advanced Find
5) Create Document Template in Sage CRM 7.1 SP2 and SageCRM 7.2