Is there a manual of government accounting for national government agencies?

Yes. The Government Accounting Manual (GAM) is prescribed by the COA to serve as guide to the accountants, budget officers, cashiers, accountable officers, and other finance personnel in recording and reporting government financial transactions.

The GAM consists of three (3) volumes as follows:

Volume I – Accounting Policies, Guidelines and Procedures and Illustrative Accounting Entries
Volume II – Accounting Books, Registries, Records, Forms and Reports
Volume III – The Revised Chart of Accounts