The Secretary of State may, if he thinks fit in any case, contribute towards the expense incurred by a local housing authority—
The contributions shall be equal to the relevant percentage of the amount of the expense incurred
The relevant percentage is—
or such other percentage as, in any of those cases, may be provided by order under section 570.
The amount of expense incurred is—
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Payment of contributions under this section is subject to the making of a claim in such form, and containing such particulars, as the Secretary of State may determine; and the contributions are payable at such times, in such manner and subject to such conditions, as to records, certificates, audit or otherwise, as the Secretary of State may, with the agreement of the Treasury, determine.