Q: "I don't have permission to see all Accounts. How do I know if an Account exists?"

A: If Account Sharing is set to Private, most users probably don't see all Accounts. But if they don't want to create duplicates, they need an easy way to look for Accounts across the entire org.

The easiest way to do this? Activate the Account Owner Report. Once activated, users can run a "magic" report that searches across the entire org, regardless of sharing model, and look at a short list of fields for those Accounts. (The Account Owner Report is located in the standard Reports folder called "Accounts".) 

The Account Owner Report displays these fields:

* These fields may not be visible in your org.

For brownie points, vote for this enhancement request. Tnx!