You may choose to do nothing and leave your account in your previous employer’s 401(k) plan. However, if your account balance is under a certain amount, be aware that your ex-employer may elect to distribute the funds to you.
While inertia is one of the primary reasons for not moving a 401(k), there may be reasons to keep it there—such as investments that are low cost or have limited availability outside of the plan. Other reasons are to maintain certain creditor protections that are unique to qualified retirement plans, or to retain the ability to borrow from it, if the plan allows for such loans to ex-employees.²
The primary downside is that individuals can become disconnected from the old account and pay less attention to the ongoing management of its investments.