This paper explores the way governments rely on budgets. Budgets are classified with reference to functions (e.g. defence, education, etc.), but expenditure from one budget (e.g. the overseas budget) can prove as effective as expenditure from another budget (e.g. the environment budget) when pursuing a specific policy goal. Are donor countries internalising spillovers by harmonising overseas aid spending with other budgetary expenditures? An empirical analysis of OECD countries (between 1990 and 2005) suggests that they rely systematically on a preferred portfolio of budgets.