SSDI applications can be filed entirely online in most cases, without ever visiting a Social Security office in person. To use the online application, your condition needs to be expected to prevent you from working for at least 12 months, or be expected to result in death — SSDI isn't designed for short-term or temporary conditions. * There's one restriction on who can use the online option: if you were denied disability benefits within the last 60 days, you can't file a new online application immediately — that situation typically calls for an appeal instead of a fresh application. * Before starting, SSA recommends working through its Disability Starter Kit, available for both adults and children under 18. It walks through exactly what documents and information you'll be asked for — medical records, work history, and details about your condition — so you're not scrambling to find things mid-application. * If online isn't the right fit, you can apply the same way people have for decades: call 1-800-772-1213 to complete the application by phone, or call ahead to schedule an in-person appointment at your local Social Security office. * One timing detail that surprises a lot of new applicants: even after approval, SSDI has a built-in 5-month waiting period. Payments don't start until the sixth full month after SSA determines your disability began — not the sixth month after you applied, which means the actual wait can be much longer once you factor in how long the decision itself takes.