Estimation of the Personal Income Tax (PIT) Gap in Poland
Estimation of the Personal Income Tax (PIT) Gap in Poland

Summary/Abstract: The literature on estimating the tax gap in direct taxes generally emphasises that using a bottom-up method produces much better results than using a top-down method. The existing methods of estimating the PIT gap using the bottom-up approach rarely take advantage of risk-based audits, which can be successfully used when tax gap estimation based on random audits cannot be applied. An important issue with risk-based audits is the potential selection bias. To address this issue, we use the Heckman selection model. We estimate the size of the PIT gap in Poland in 2017 by using data from the tax filings of taxpayers earning income from business activities taxed at a flat 19-percent tax rate and risk-based audits. Our findings show that the predicted PIT gap corresponds to 4.5 percent of the total tax liability of this group of taxpayers. We also identify the regions and sectors with the highest predicted PIT gap per taxpayer. Our results show that the Heckman model can be used as a tool by tax authorities to improve the efficiency of risk-based audits.

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