Question: Which of the following sentences is better to use?

> 
> 1. Where it is concluded that the report is incorrect it will be returned.
> 2. If the report is incorrect then it will be returned.
> 
> 
> 

Or do they mean the same thing?

These sentences will be used for a description of activities.

Answer: 
In your examples, the sentence starting with *if* is easier to understand. But it always depends on the context of what's being written as well as target audience. I find *where* is used more often in formal writings, but not always.
**If**.

If you use *where*, the sentence is harder to parse. You run the risk of confusing your audience, who might think that you're talking about a location.