Which disability benefit applies to you?
Age and nation decide which benefit you claim, and the four systems are not interchangeable. Answer two questions to see which one applies and where the official page for it is. Nothing is stored, and this names the route rather than estimating what you would receive.
Pick an age and a nation to see the route.
If a decision has already been made
A decision you disagree with follows a separate route from a first claim. In England and Wales that is a mandatory reconsideration and then an appeal, both on a one calendar month clock. Work out your dates with the free deadline checker, or read the mandatory reconsideration guide. In Scotland the equivalent first step is a redetermination by Social Security Scotland, and in Northern Ireland the process runs through the Department for Communities.
Free, independent advice on any of these routes is available from Citizens Advice and local welfare rights services.
General information and document drafting, not benefits advice. Check the linked official pages before you apply, because rates and rollout dates change.