This study has the objective of identifying the challenges militating against the growth of tax-to-GDP ratiosof sub-Sahara African countries,their causes and remedies. Nigeria is used as a case studywhile the content analysis research approach is adopted.Reports from some apex international monetaryauthorities indicate that, while a typical advanced country has a tax-to-GDP ratio of around 40% , manysub-Sahara African countries maintain tax-to-GDP ratios that fall below the 15% threshold..Though the tax structures in many of thosecountries have improved in recent times, growth in their domestic revenue mobilization has been generally sluggish.Many of them persistently experience significanttax-gaps,overwhelming incerase in external debt-to-GDP ratio and budget deficits -a clear manifestationthat their tax policiesrequire serious overhauling. The paper reveals that the low-rated countries are characterized by Gulf countries while the high rated ones are dominated by European countries and that, even as one the largest economies in Africa, Nigeria is one of the sub-Sahara African countries having the lowest tax-to-GDP ratios. It suggests that, in line with best practices, thesub-Sahara African countries should put in place clear political mandates to tackle low levels of tax payment and a simpler tax system with a restricted number of rates and exemptions.