One way would be to have nice, organized requirements and a traceability matrix. This way, at least you can check that every requirement is traceable at the design level (or even further).
If you're using OO Programming, there are some criteria to check the design. If you're using some automated tools for design, it would be a lot easier.
Otherwise, you can if you're at least so experience as the designer.
But, anyway at least some peer review could help.
If you need a reason to be happy - FIND IT, don't wait it !
If you have good design knowledge you can refer to the external and internal specifications (major part) of the software. You can suggest your development team to use tools like Visual Modeler from Microsoft.