How to inactive Items?

Dear All Experts,

We have thousands of duplicate items in our ebs system. Now we need to identify that which items are opened as duplicate.

The issue which we are analyzing that we have purchasing, inventory, asset tracking, project costing and fixed assets modules along with other financials modules. Now all items will be in the system along in those modules also.

So what will be the best approach to handle this situation and inactive the items with balance of all items transfers.

Thanks in Advance....