Note well that one full week of housing benefit is not paid meaning every tenant will go at least one week in arrears which also adds to the one week all tenants are likely to be in arrears anyway as all weekly tenancy agreements are a week in advance.  So given you have to survive for 44 days which is 7 rent weeks then if you cannot pay any rent in this waiting period you will be 9 weeks in arrears when the first  payment arrives.

Unless you can pay more than 5 weeks rent payment while awaiting the first UC payment then you will be more than 4 weeks in arrears and the landlord can – and will – request a managed payment which is the rent direct PLUS up to 20% of your standard UC payment on top of this.

As such when you get your first UC payment it will be between £45.91 less than expected or up to £147 less than expected which is the range of 10% for a single standard UC amount up to 20% of the couple standard UC rate for this 44 day period.  Note that this is double to quadruple the amounts deducted at source from welfare benefit under the current system.

Read more at: SPeye Joe (Welfarewrites)
Joe Halewood writes about welfare rights and welfare reform

44 days before the first UC payment received.