Housing Costs - Deadline for applying

I am currently working with leaseholders advising them on their benefit entitlement.  Most of my clients have service charges and repair costs which they can claim as housing costs through their Pension Credit, ESA or IS/JSA claims however I would like some clarification on the deadline for submitting housing cost claims to be considered.  One of my clients has been turned down for housing costs for repairs on her property as she did not submit the final account for the repairs within 52 weeks of receiving the bill (she had not realised that she could claim for the repairs).  While I understand there must be a deadline I cannot find anywhere where is states that it must be 52 weeks, could someone let me know where I could get this information.

Secondly, I am aware that when they do pay housing costs for repairs they pay the bill on a monthly basis over the course of a year therefore if a client submits the bill 11 months after they receive it does that mean they only get one months installment or is the deadline just to get the bill in and they will pay over the following year?