It is commonly believed that government faces a budget constraint according to which its spending must be “financed” by taxes, borrowing (bond sales), or “money creation”. Since many modern economies actually prohibit direct “money creation” by the government’s treasury, it is supposed that the last option is possible only through complicity of the central bank—which could buy the government’s bonds, and hence finance deficit spending by “printing money”.
Actually, in a floating rate regime, the government that issues the currency spends by crediting bank accounts. Tax payments result in debits to bank accounts. Deficit spending by government takes the form of net credits to bank accounts. Operationally, the entities receiving net payments from government hold banking system liabilities while banks hold reserves in the form of central bank liabilities (we can ignore leakages from deposits—and reserves—into cash held by the non-bank public as a simple complication that changes nothing of substance). While many economists find the coordinating activities between the central bank and the treasury quite confusing. I want to leave those issues mostly to the side and simply proceed from the logical point that deficit spending by the treasury results in net credits to banking system reserves, and that these fiscal operations can be huge. (See Bell 2000, Bell and Wray 2003, and Wray 2003/4)
If these net credits lead to excess reserve positions, overnight interest rates will be bid down by banks offering the excess in the overnight interbank lending market. Unless the central bank is operating with a zero interest rate target, declining overnight rates trigger open market bond sales to drain excess reserves. Hence, on a day-to-day basis, the central bank intervenes to offset undesired impacts of fiscal policy on reserves when they cause the overnight rate to move away from target. The process operates in reverse if the treasury runs a surplus, which results in net debits of reserves from the banking system and puts upward pressure on overnight rates—relieved by open market purchases. If fiscal policy were biased to run deficits (or surpluses) on a sustained basis, the central bank would run out of bonds to sell (or would accumulate too many bonds, offset on its balance sheet by a treasury deposit exceeding operating limits). Hence, policy is coordinated between the central bank and the treasury to ensure that the treasury will begin to issue new securities as it runs deficits (or retire old issues in the case of a budget surplus). Again, these coordinating activities can be varied and complicated, but they are not important to our analysis here. When all is said and done, a budget deficit that creates excess reserves leads to bond sales by the central bank (open market) and the treasury (new issues) to drain all excess reserves; a budget surplus causes the reverse to take place when the banking system is short of reserves.
Bond sales (or purchases) by the treasury and central bank are, then, ultimately triggered by deviation of reserves from the position desired (or required) by the banking system, which causes the overnight rate to move away from target (if the target is above zero). Bond sales by either the central bank or the treasury are properly seen as part of monetary policy designed to allow the central bank to hit its target. This target is exogenously “administered” by the central bank. Obviously, the central bank sets its target as a result of its belief about the impact of this rate on a range of economic variables that are included in its policy objectives. In other words, setting of this rate “exogenously” does not imply that the central bank is oblivious to economic and political constraints it believes to reign (whether these constraints and relationships actually exist is a different matter).
In conclusion, the notion of a “government budget constraint” only applies ex post, as a statement of an identity that has no significance as an economic constraint. When all is said and done, it is certainly true that any increase of government spending will be matched by an increase of taxes, an increase of high powered money (reserves and cash), and/or an increase of sovereign debt held. But this does not mean that taxes or bonds actually “financed” the government spending. Government might well enact provisions that dictate relations between changes to spending and changes to taxes revenues (a balanced budget, for example); it might require that bonds are issued before deficit spending actually takes place; it might require that the treasury have “money in the bank” (deposits at the central bank) before it can cut a check; and so on. These provisions might constrain government’s ability to spend at the desired level. Belief that these provisions are “right” and “just” and even “necessary” can make them politically popular and difficult to overturn. However, economic analysis shows that they are self-imposed and are not economically necessary—although they may well be politically necessary. From the vantage point of economic analysis, government can spend by crediting accounts in private banks, creating banking system reserves. Any number of operating procedures can be adopted to allow this to occur even in a system in which responsibilities are sharply divided between a central bank and a treasury. For example, in the US, complex procedures have been adopted to ensure that treasury can spend by cutting checks; that treasury checks never “bounce”; that deficit spending by treasury leads to net credits to banking system reserves; and that excess reserves are drained through new issues by treasury and open market sales by the Fed. That this all operates exceedingly smoothly is evidenced by a relatively stable overnight interbank interest rate—even with rather wild fluctuations of the Treasury’s budget positions. If there were significant hitches in these operations, the fed funds rate would be unstable.