Implementation Verification
Running calculations and periodic processes is the only way to verify that the plan produces the needed results. Be sure to thoroughly test each aspect of the calculations under a variety of conditions: employees with long and short service, with interrupted service, employees who moved in and out of eligibility, and as many other situations as you deem significant. If there are grandfathered rules, or frozen benefits because of regulatory changes, make sure that these are being properly applied as well.
Do not underestimate the importance of thorough testing.