I was specific enough to mention "escrow". Has Dr. Feige considered tax avoidance in his paper? Has he factored it into his calculations?
Simply put, yes, Dr. Feige appears to have thought this out and tried to account for everything possible. Tax evasion is covered in Section 5.4 if you have time to look into it.
"5.4. Tax evasion
Tax evasion is a major cost of the present tax system. The IRS (1988) projected 1992 unreported legal source income on individual income tax returns at $587 billion. Feige’s (1996, 1997) estimate of combined legal and illegal source unreported income for 1992 was $696 billion, giving rise to an estimated tax gap of $123 billion in that year.20 The General Accounting Office (1997) estimated the 1992 tax gap to be $128 billion.In addition to the macroeconomic consequences of this lost revenue, evasion has unintended distributive consequences, notably, it redistributes income from honest taxpayers to dishonest evaders and from middle income groups to both poor and rich.
Every tax can be avoided and evaded. The question is, at what cost? Since the APT tax is collected through the payment mechanism, it can be avoided by engaging in barter transactions. Except in very rare circumstances, barter is so costly as to reduce this loophole to insignificant
proportions.
Tax evasion through “offshore” cyberspace exchanges poses a more subtle problem that can be addressed by structuring appropriate penalties that provide serious disincentives for this type of evasion. The first of these contemplated by the APT tax proposal is to deny the parties to any untaxed transaction the right to enjoy the legal protections of the state. Therefore any “offshore” exchanges of property rights can be denied all of the benefits and protections of the “rule of law” in the nations that have established the APT tax. A second device, proposed by Kenen (1996) is to apply the tax at a penalty rate to all transactions made with financial institutions residing in tax free jurisdictions.
A more severe penalty would be for APT tax compliant nations to simply refuse to recognize any and all credits or debits from “offshore” havens or non APT countries that countenance “counterfeit” financial intermediary transaction exchanges. Every “offshore” exchange must have points of connection with the payment and clearing systems of the world’s important legitimate financial markets. But these connection points are also the Achilles heel of “offshore” tax havens, since once severed, the tax haven ceases to function. The force of this sanction grows in importance as more states adopt the APT tax regime.
The rapid expansion of Internet commerce poses special threats to the integrity of present tax collection systems. Under the APT system, Internet transactions that are paid by credit, debit or stored value cards pose no collection problem. Credit and debit card payments are taxed when the customer settles accounts with the card issuer and stored value cards are taxed when they are recharged with a debit to a financial account.
Technological innovations such as the creation of anonymous forms of E-cash (digital cash) that represent a private digital substitute for the government’s present monopoly of issuing currency can raise collection problems even for an APT system. Such E-cash could accumulate and simply be transferred from party to party without returning frequently to the banking system. If anonymous private digital cash is permitted to substitute freely for government paper currency, it can function as a tax evasion vehicle. Private digital cash also deprives taxpayers of annual seigniorage earnings of the Federal Reserve that are now returned to the US Treasury. Given these concerns it behooves the government to issue its own E-cash that would benefit from the natural network externalities that now accrue to paper legal tender. Under the APT system, the creation of private inside money designed to evade taxes would be illegal and treated as would be any attempt to counterfeit legal
tender."