Is it best to tell them as soon as you start or wait until the first wage has been paid?
My assessment period runs from 18th of July-17th of August. I’m not sure yet when I will be paid as it’s fortnightly but not sure when exactly it’s paid. If I tell them straight away will they change my claim straight away?
Tell them the day you start, or a few days in and date it for the day you started. They will not take any money until they receive details of your payslip, this is how they work out how to adjust your payment. They will never change anything beforehand because they won't know how much you'll be getting paid.