"… a person who makes a claim, or a person to whom housing benefit has been awarded, shall furnish such certificates, documents, information and evidence in connection with the claim or the award, or any question arising out of the claim or the award, as may reasonably be required by the relevant authority in order to determine that person's entitlement to, or continuing entitlement to, housing benefit, and shall do so within one month of being required to do so or such longer period as the relevant authority may consider reasonable."
"Where, by, or in consequence of, any provision of these Regulations or Schedule 7 to the Act [ that is theChild Support Pensions and Social Security Act 2000 ] – …. (b) any notice … or other document is required to be given or sent to any person other than the clerk to an appeal tribunal, the Secretary of State or the relevant authority, as the case may be, that notice or document shall, if sent by post to that person's last known address, be treated as having been so given or sent on the day it was posted."