I work in financial services in the UK as a business analyst. I am currently on a project that has a second "big" consultancy to do the work. 

The first one was kicked out, they were photoshopping the test evidence (screenshots) and hiding the defects (yes it was one of the big 4) the system had so many defects the programme had to go into a "stabilisation" programme to sort out the mess. The second "big" consultancy has a contractual obligation to allow the business analysts access to the system and (read-only) access to the test database. 

The second consultancy was also providing test evidence with screens shots with no commentary. I have found the test evidence showing the code defects where the coder has changed the format of the field content (Was: yyyy-mm-dd To: yy-mm-dd 
 oo:oo:oo:oooo) and he thought it was ok. The tester just did a screenshot and passed it. I have rejected this and provided a test evidence template. 

The template requires the user story details, the acceptance criteria, above each test case they need text to explain what the test is about, the before and after versions of only the screens that have changed. An extract of the relevant test record from the database. 

I don't trust what they deliver because of what I have found, not once but many times. So documented test evidence is critical to proving a system.

Template layout: 
This provides a good set of test evidence - accurate, only what is needed and complete. This enables you to trace the test back to the requirements. 

 - Test to be performed 
 - Testers name & date of test
 - User story
 - Acceptance criteria
 - Text explaining what is specifically being tested
 - Before: Screenshot of screen being changed
 - After: Screenshot of screen being changed
 - Before: DB extract of the relevant record
 - After: DB extract of the relevant record