Discretionary leave to remain extension - Documents

Hi everyone.

My wife is on a 3 year DLR. She received that instead of ILR.
I would like to know what documents I would have to send
When applying for an extension.

Thank you.

On what basis did she get the DLR.

Because she did not have the English requirements for ILR she was given DLR for 3 years.

Do I need to send bank statements etc. I am not working I am on ESA.