Tax-backed Bonds

I’m intrigued by this idea. But I don’t think it works. Suppose the government defaults on its debt. I can now use my €1,000 bond to pay my taxes. But what does the government do with the bond which is now sitting in the tax-collector’s office? It’s not money. It can’t be used to pay nurses and firemen. So how is the day-to-day spending of the government to be funded? Pilkington and Mosler do not say.