Rosie
See the following FAQ as to which documents to request
ESA medical – what forms to ask for? The DWP use your National Inssurance Number to decide which day you should be paid, see the following FAQ
Benefit payment dates If today was your prescribed pay day, then you should contact the DWP on Monday if you have still not been paid. For an automated system, which should not human intervention, it fails to pay claimants quite regularly
Gordon