<Your address>
<Postcode>

14 April 2016

<Address of the housing benefit department>

Dear Sirs,

Re: Housing Benefit claim change of circumstances – insert name, and reference or account number> 
(you will find this on any letters from the housing benefit department)

I am writing to notify you of a change in my circumstances from <date that your circumstances changed>. The change was <state what the change has been>.
Please update my claim accordingly. Should you require any further information or if I am required to complete a new application please do not hesitate to contact me.
Thank you for your assistance in this matter. 
Yours faithfully,

<Your name>
<Your contact telephone number>