No one wants to pay for something they don't need. And if they do need it, they certainly don't want to pay more than they have to. That's why you should weigh the pros and cons of voluntary benefits carefully before committing to them.
Voluntary benefits are insurance policies and other coverages that are offered through an employer but aren't subsidized by them -- like dental and vision coverage, supplementary life insurance, accident insurance, and short- and long-term disability. When you purchase these benefits through your employer, the premiums will be deducted from your paycheck, which makes things easy for you. But just because it's easy doesn't mean it's a good deal.
Before signing up for a voluntary benefit, ask HR if you're getting it at a discounted rate and if there's any real advantage to purchasing it through them. Then ask yourself if the benefit duplicates an insurance or service that you already have and whether it's really worth your money. For example, what use is vision coverage if you're young, single, and every checkup you've had since childhood has been perfect?
And never sign up for a voluntary benefit that you could get somewhere else for a better rate.