National Treasury Act Article 21

At the end of the fiscal year, the unused balance of the allocated budget of each agency, except those payables which already incurred but not yet paid, and which have been approved for retention, the rests shall be immediately stopped for payment, unless otherwise provided by law.For the unused balance which is safekept and used by the agency itself, it shall also follow the regulations in stipulated in the preceding paragraph and stop the payment, and return back to the National Treasury immediately after the end of the fiscal year.