If you work for a company that provides its employees with group disability income insurance, benefits typically replace a fixed percentage of your salary, say, 50 percent. So if you get a raise, your disability benefit will automatically adjust upward. An exception would be if you are a fairly well compensated employee and your income already places you at your company's maximum monthly cap for disability payments, often set around $4,000 or $5,000. In these instances, if you get a raise and you're concerned about the loss of income that would occur if you were to become disabled, you can always seek to supplement your group coverage with an individually purchased policy.
If you work for a company that provides a group benefit but decide to go into business for yourself, you'll definitely want to consider buying individual coverage. Because if you were suddenly unable to work, there now would be no employer-sponsored safety net to fall back on. For the same reason, if you're self-employed and your income increases significantly, you probably should increase coverage you already own or purchase a supplemental policy.