If you disagree with a benefits decision by the DWP or HMRC, you can ask for it to be looked at again.
This is called a mandatory reconsideration. It means another person will look at the decision and see if it can be changed.
You must go through this stage before you can appeal.
Usually, you have to ask for the mandatory reconsideration within one month of the date on your decision letter. Or the message in your online account if you’re claiming Universal Credit.
If you miss the deadline, the department making the decision doesn’t have to accept your request unless you had a very good reason. For example, you were in hospital, or a close relative died.