“Government budgeting” is one of the few lines in the GS III syllabus that UPSC names in two words, and it is tested every year in some form. Prelims asks the vocabulary: revenue vs capital, the four deficits, the three funds, and how Parliament passes the Budget. Mains asks about fiscal consolidation, the quality of expenditure, and Centre–State fiscal relations.

What UPSC asks

Prelims: revenue and capital receipts and expenditure, fiscal, revenue, effective revenue and primary deficits, the Consolidated Fund, Public Account and Contingency Fund, charged expenditure, vote on account, cut motions, FRBM targets, the Finance Commission.
Mains GS III: fiscal consolidation vs growth, the debt anchor, subsidies and capital expenditure, outcome and gender budgeting, fiscal federalism.

Key sub-topics

Sub-topic	What to master
Fiscal policy	Functions, instruments, multiplier, crowding out
The Constitution	Articles 110, 112–117, 265–267, 280, 292–293
Budget process	Stages in Parliament, cut motions, guillotine
Budget structure	Revenue and capital account; receipts and expenditure
Deficits	Revenue, effective revenue, fiscal, primary, monetised
Rules	FRBM Act 2003 and its amendments; N.K. Singh Committee
Reforms	Merger of the Railway Budget, 1 February date, end of Plan/non-Plan

Start with The Union Budget and Fiscal Deficits, then revise with the quick revision sheet and practice questions.