There is a formal appeal process if you want to challenge a decision about universal credit

This part of the website explains how universal credit works if you are self-employed.

Your pay as an employee will usually affect the amount of your universal credit award. In most cases, information about your pay (as an employee) will be sent to DWP and DfC automatically from HMRC and this page looks at how that information is used and in which assessment period.

If you are claiming universal credit you will usually be placed into a work-related group. Each group has different work-related requirements. Some people will be placed in the no-work related requirements group. Your claimant commitment will show which group you have been placed into and what is ...

Universal credit awards are made up of a number of elements. This page explains how universal credit awards are calculated. 

Universal credit awards are made up of a number of different elements. The elements that are included in your award depend on your circumstances (and your partner’s circumstances if it is a joint claim).