The changing dynamics of tax revenue and its responses to domestic and external shocks play a pivotal role in the discussion of the sustainability of public finance in small developing economies. However, the empirical literature on the response of tax revenue to various shocks in developing economies in the Pacific is sparse. Despite several tax reforms over the last decade, the spending plans of the Fijian government since the 2017/2018 budget announcements have stimulated frequent public discussions regarding the sustainability of public debt. Against this background, the main purpose of this paper is to investigate the response of tax revenue in Fiji - a small developing island economy, to external and domestic shocks using historical annual data covering more than five decades. This study uses unit root tests that account for single and multiple endogenous structural breaks and finds that tax revenue in Fiji is a non-stationary process, I (1) with break dates coinciding with tax reforms, general elections, and political coups. The findings reveal that tax reforms and political developments are possible important sources of shocks to tax revenue and have important policy implications. First, shocks to tax revenue will have persistent effects, with the effects of adverse shocks being transmitted to other related variables and sectors of the Fijian economy. Second, historical values of tax revenue cannot be used to formulate forecasts of tax revenue and policymakers should consider other determinants of tax revenue (for example, the share of the agriculture sector, trade volume, political stability, education, life expectancy, infant mortality rates, age composition of the population, urbanization, inflation rate, and corruption) for forecasting purposes. The evidence of non-stationarity indicates that future studies on tax revenue need to carefully reflect on the modeling technique to avoid spurious regressions. Furthermore, our findings reveal that temporary fiscal measures will not have a permanent effect on tax revenue and sustainable revenue growth requires focusing on long-term (rather than short-sighted) reforms. Thus, our findings underscore the importance of evidence-based policy reforms to improve the resilience, efficiency, and sustainability of the tax system in Fiji to shelter it from future adverse shocks. [ABSTRACT FROM AUTHOR]