I was inspired by your quote "I want your opinion", because I proposed the establishment of the Citizens Suggestions Processing Centre back in 1995 as an electronic suggestion box with a single point of entry.
I would like to propose here a fundamental solution for the underground economy at the source. The first element is to abolish the use of cash in favour of electronic commerce and credit/debit cards. The second element is the replacement of the Goods and Services Tax (GST) with the Transaction Tax. The Transaction Tax, much like a domestic "Tobin Tax", would apply to any transfer of money from one bank account to another bank account bearing a different name without exception. The rate of the Transaction Tax would be set much lower than the GST, yet the tax would be revenue-neutral because it covers broader base than just goods and services. The underground economy would disappear, business processes would be simplified, and the Liberal Government could finally claim that they killed the GST.
I believe that the computer technology has advanced enough to handle this type of tax at financial institutions when the rush to fix the Y2K bug is over.
P.S. Please do not hesitate to check out my proposals and opinions over the years concerning public policies. These innovative ideas can be found at the following webpages.