Hi cw12
Here is the official guidance on UC payments-
Days and payments
Your payments will usually be calculated from the day you submit your claim and you will get your first payment 7 days after the end of your first assessment period.
Your payment will then be made on the same date every month while you remain entitled to Universal Credit. If your payment date is on a bank holiday or weekend you will be paid on the last working day before the bank holiday or weekend.
David
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
