How often do the accounts of these councils need to be audited by the Comptroller and Auditor-General?
The accounts of the District Council or, as the case may be, the Regional Council shall be kept in such form as the Comptroller and Auditor-General of India may, with the approval of the President, prescribe. The Comptroller and Auditor-General shall cause the accounts of the District and Regional Councils to be audited in such manner as he may think fit, and the reports of the Comptroller and Auditor-General relating to such accounts shall be submitted to the Governor who shall cause them to be laid before the Council.]

From this passage, we can deduce that the accounts need to be audited by the Comptroller and Auditor-General, but there is no specific frequency mentioned.