Duplication shouldn't occur unless, somehow, you had multiple records of the same client in the tax product(s) you used at some point in time.

If you are absolutely, positively, 100% sure which record in Link is a duplicate that should be "deactivated", so to speak (but not technically as you'll see what I mean), and that duplication does not exist in your tax product (i.e. ProSeries), there is a function in Link you can use.

1. Click on the gear icon on the top-right corner next to your company name;
2. Select Firm > Manage Clients;
3. On the line of your duplicate client, click on Mark as Inactivate under the ACTIONS column; and
4. Read the warning in the popup and click on the Yes, mark as Inactive button.