Tax revenue does indeed fund the budget of any government that does not have its own currency, like Panama, or any state or municipality. But it is entirely inaccurate to characterize tax revenue as the source of funding for any federal government that creates its own currency. Do you know what such governments do with the tax they receive? They simply destroy it. That's right. All tax revenue received by currency producing governments is nothing more than an accounting entry that effectively reduces the circulating money supply. It pays for nothing. So the argument that governments suffer an economic loss due to tax havens is specious at best and largely untrue because such 'revenue' is not a source of income. It is the government that produces the currency, therefore it does not rely on taxation to supplement its accounts. Taxation by currency producing governments serves only to reduce the circulating money supply, which may be necessary to quell incipient or extant price inflation. Taxation by currency producing governments is effective only as a way to slow the economy or punish certain social or economic sectors.