<Your address>
<Postcode>

09 October 2020

<Address of the housing/council tax department>

Dear Sirs,

<Your reference or account number> 
(you will find this on any letters from the housing and council tax 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 please do not hesitate to contact me.
Thank you. 
Yours faithfully,

<Your name>