This page explains when it is possible for tax credit awards to be backdated.

Tax credit awards are made up of a number of elements. The amount of any award depends on the elements that are included in the award and the household income.

Child tax credit is paid by HM Revenue and Customs (HMRC) to support families with children. It is paid independently of child benefit and is payable whether you are working or not.

Tax credit awards are made up of different elements, including elements that provide additional financial support for people with disabilities or long-term health problems. This page explains the disability element and the severe disability element of working tax credit. There are separate elements ...

Working tax credit is paid by HM Revenue & Customs (HMRC) to support people who work and are on a low income. It does not matter whether you are an employee or self-employed. 

The minimum income floor applies to some universal credit claims if you are self-employed. It does not apply in all cases. If the minimum income floor applies, you may be treated as earning a certain amount even if your actual earnings from self-employment are lower.