They also invest in an IRA
People who invest money through both a 401(k) and an IRA have balances that are three times higher on average than those who save in just a single vehicle, Fidelity says. A common misperception holds that you can only invest in a 401(k) plan or an IRA, not both. But for the vast majority of income earners that’s not true. So, if you have extra cash, put it to work.