چكيده لاتين :
In this paper the relation of underground economy and tax gap in
Iran has been examined. The results show that the underground
economy size is almost 20 percent of GDP in Iran. In this research
three methods of estimation of underground economy size has been
used and combined to achieve a more precise estimation. The
methods that have been used are: cash, fuzzy and latent variable
methods. The size of tax gap in Iran has been over 30 billion dollars
in recent years. Some new payment systems as ATM cause change in
money velocity which makes it necessary that new factors to be taken
into account
