IMF Proposes Reverse Method for VAT Compliance Gap Estimation

The IMF's Fiscal Affairs Department and the International Finance Corporation proposed a Reverse Method as a new, simplified, and cost-effective way to estimate VAT compliance gaps. Considering the challenge of determining the amount of VAT governments fail to collect, primarily due to tax evasion deliberately concealed, the IMF suggests a new method, in addition to detailed national data and complex modelling, such as standard RA-GAP assessments.

Key Features of the IMF's Reverse Method

Although the IMF developed the RA-GAP, a global benchmark for measuring VAT gaps, which produces detailed VAT gap estimates based on national accounts and tax administration data, it determined that this method is expensive, data-intensive, and not easily repeatable over time or across countries. Consequently, the underlined constraints limit its use for broad, regular international comparisons, creating a monitoring gap that the new Reverse Method aims to close by offering a simpler and more scalable alternative.

The IMF noted that when applied to 111 countries over the period 2010 to 2023, the Reverse Method reveals clear cross-country and income-group patterns. More specifically, the method showed that advanced economies and low-income countries exhibit gradual improvement in VAT compliance over time, suggesting more vigorous enforcement or better system design. In contrast, emerging market economies display broadly stagnant performance.

The new method is an indirect approach based on the concept of C-efficiency, which measures the ratio of actual VAT revenue to the revenue that would be raised if all final consumption were taxed at the standard rate under full compliance. Instead of estimating compliance gaps directly, as is done in traditional models, the Reverse Method intentionally inverts this logic. It starts from observed C-efficiency and a separately estimated policy gap, and then attributes the remaining difference to non-compliance. 

Conclusion

Under the new method, even in the absence of detailed administrative data, the governments may estimate VAT compliance. As a result, governments will understand the scale of VAT non-compliance, indicating how much revenue is lost to evasion and administrative weaknesses, and how much could realistically be recovered through better enforcement and policy design.

Notably, the IMF highlighted that the Reverse Method is not intended to replace detailed, country-specific VAT gap studies, but rather a high-level screening and monitoring instrument that complements more granular analyses.

Source: IMF - Technical Notes and Manuals