Real estate, Huge retail, wholesale, distribution, supply, dairy, agriculture, tourism, movie production, music industry, actors, medical industry etc. Except for registered companies, firms, Salaried class ... most of other trades are not registered nor they file their tax returns.
The problem is and remains that Pakistan has a very sophisticated online tax filing system, but the taxman and the tax payer are not educated enough to use and implement it properly to get the maximum benefit from it.
Middle finger to your opium and prostitution guesses, I am sure you hardly know anything about what BayNami is in Pakistan.
The reason Pakistan relies heavily on indirect taxation and withholding of income tax.
Tax evasion != Undocumented economy
The agriculture & dairy output is known unless you are claiming there is production outside of official numbers. Ditto for the number of tourists. The movie industry is fixed in terms of number of movie tickets sold.
for years construction industry to the motor industry are all undocumented ... a main source of income to buy tangible to fixed products is unknown... and lots of other trades .. sugar mafia and the list goes on....both opium and prostitution should be taxed like US and Canada. What do you think ?
the production of sugar is known. tax evasion != undocumented economy