Housing Benefit and UC

In another questioner’s post regarding moving to another borough David wrote:

”If you currently receive Housing Benefit you should get a 2 week run on after claiming UC.”

Can you explain what that means please. My son, whom I am Appointee for, gets Housing Benefit for his current flat, the landlord is a Housing Association/social housing landlord so all the rent is paid directly to the landlord apart from some of the service charges which my son pays. The rent is paid by Housing Benefit 4 weekly in arrears. My son will be moving borough at some point. When he’s coming up to the date of moving I should surely tell the current borough that his current tenancy will be ending on a particular date. Then the date he moves to the new borough I will claim UC and send them a copy of the new tenancy…the flat is again with Housing Association/social housing landlord.

Hi - my question is to do with David's response that with Housing Benefit "you get a 2 week run on after claiming UC". This makes no sense to me because Housing Benefit covers a specific tenancy in one borough, and since it's paid in arrears to the landlord it should be paid for that period of arrears - how can Housing Benefit in one borough cover another tenancy in another borough where the person is moving to and claiming UC ? Housing Benefit isn't like these other benefits, it's specific for a particular tenancy.

Thank you David - that makes complete sense now, I'd got the impression it was someone moving from one borough to another.