A refund claim shall be approved or denied: under § 14-904 of this subtitle, by the Comptroller; under § 14-905 of this subtitle, by the appropriate collector; or except as provided in subsection (b) of this section, under § 14-907 or § 14-908 of this subtitle, by the Department, clerk, or the Director of Finance that collected the tax. If a refund claim made under § 14-907 or § 14-908 of this subtitle is not allowed and is not denied on or before 6 months from the date the refund claim is submitted, the person submitting the claim may treat the claim as denied. If a refund claim is made under § 14-907 or § 14-908 of this subtitle, the Department, clerk, or Director of Finance considering the refund claim shall: investigate the claim; notify the claimant of an opportunity for a hearing on the claim; and if the claimant requests a hearing on the claim, conduct a hearing. If a claim is determined to be eligible for refund, the agency considering the claim shall request authorization of payment for a claim under: § 14-904 of this subtitle, from the Comptroller; § 14-905(a) of this subtitle, from the appropriate county or municipal corporation official; or § 14-907 or § 14-908 of this subtitle, from the Comptroller or the chief fiscal officer of the county. The agency determining a claim made under § 14-907 or § 14-908 of this subtitle shall give written notice to the claimant of: a denial of the claim by that agency; a denial of payment authorization under subsection (d)(3) of this section by the Comptroller or chief fiscal officer of the county; or a delay in paying an approved claim.