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.

For universal credit, if you are an owner or director of a limited company you may be treated as though you are self-employed and the company income treated as your self-employed income. 

The benefit cap is a limit on the total amount of working age benefits that you can receive. If your universal credit is over the amount of your benefit cap, it might be reduced.

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.

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).