Group disability insurance is a popular employee benefit, and rightfully so. Disability insurance pays a portion of your regular income if you become disabled and cannot work.

But you could be setting yourself up for financial trouble if you think your group policy will take care of all your needs. You may need additional coverage through an individual disability insurance policy to provide an adequate safety net.

Here are four facts about group disability coverage you should know:

1. The insurance income could be less than you think

A group disability policy typically pays 60 percent of your income. But if the employer pays the premium on the policy, the insurance money is taxable, so you receive 60 percent of your income minus taxes.

In addition, that 60 percent mark applies only to your base salary--it does not include commissions and bonuses.

2. You may not be covered for partial disability

Partial disability occurs when you can work, but not full time. Some group policies cover partial disability for a limited period, such as six months. Others don't cover it at all. Without coverage for partial disability, you would get no reimbursement for lost income as a result of having to work part time.

3. Coverage could disappear

The insurance company can terminate the policy if a company experiences too many expensive claims. Or, the employer can decide to discontinue the employee benefit to cut costs. You have no control over these decisions. The only way to control your disability insurance coverage is to purchase an individual policy tailored to your needs.

4. Insurance money can't go toward a 401(k)

Only earned income--not money paid by an insurance policy--can be contributed to a 401(k). This may not be a serious issue if you're out of work for only a few months, but it could be a problem if you're out of work for years. You can purchase riders on individual disability insurance policies to provide money toward retirement savings.

Most employees are unaware of what their group disability policy covers. Get the details about your coverage and talk to a financial adviser to see whether you need additional insurance. The Council for Disability Awareness offers free tools on its website to help you plan, including a Personal Disability Quotient, which reveals your chance of becoming disabled; and a Financial Security Plan, which helps determine whether you've prepared a strong safety net.