An employment verification is often an overlooked part of the reference check or background check. It is not a good idea to treat this lightly. You can attempt to do this yourself or hire a service to do it for you.
Many times when you try to check on the employment record of a candidate you end up contacting human resources and they are hesitant to give over too much information. This leads to reluctance by some to even attempt this type of check.
While it is true that often you can not get someone to talk about a candidate, there are some things you can often get from a former company. The best strategy is to sympathize with the person and let them know you understand. Let them know you've worked in companies where they don't like to give too much info either. Then transition into it is so hard these days to get good references etc. etc. Sometimes you can warm them up.
Even if you can not get what you are looking for in an employment check you can get valuable information. Here's what you should be able to get;
Why are these valuable? The first three allow you to verify the accuracy of the resume. The second two give you two things, first if there was any significant change in salary you can assume the candidate performed well and was rewarded with higher pay. Second, if it is a recent position, should you decide to make an offer you can see some salary history on which to base an offer.
One final thought, sometimes for expediency you can include employment verification as part of a background check. The incremental charge is nominal though you will only get the start/end date, salary info and job title etc.
In the end, it is valuable to verify a candidate's employment history if for no other reason than to check dates on an application or resume and get salary information should you decide to make an offer.
This prevents future misunderstandings. Perform this check at the front end so everyone starts on the same page with the right information.