CMS do no care about the person paying, they will take the word of the receiving parent over evidence from the paying parent. The benefit system sees way too many people abusing it, such as having working partners living in the same house while claiming HB and such. So much more is on offer for workshy people than the actual people who work low paying jobs. If you're on benefits or rich then the UK Gov will 100% back you and keep giving you free stuff.