In recent years, computer games have gained widespread popularity, driven by technological advancements and internet expansion, leading to the prevalence of on-line gaming and the decline of physical media. The taxation of these games has become a debated issue, particularly regarding the differentiation between off-the-shelf and custom software. In 2021, the Brazilian Supreme Federal Court deemed software taxable as services. Uncertainties have arisen regarding in-game transactions, encompassing the acquisition of goods, rights, or financial operations. This article aims to understand whether transactions in on-line games qualify as the acquisition of goods or services, determining the applicable taxes, considering the Brazilian legal landscape post-Tax Reform. Specific objectives include grasping technical distinctions between goods, commodities, and services; conceptualizing and distinguishing software and on-line games from a technological perspective; outlining types of transactions in on-line games to support their legal classification; understanding the Supreme Court's rationale on software as services; and analyzing the impact of the Tax Reform on the taxation of in-game transactions. The research, characterized as pure and explanatory, employs a qualitative approach, deductive method, and bibliographic/documentary procedures. It concludes that the accurate taxation of on-line gaming transactions is a significant source of legal uncertainty, stemming from the classification and legality of tax incidence. The Tax Reform, by instituting a single tax for operations involving goods, services, and rights, holds the potential to resolve these uncertainties, rendering unnecessary the determination of the nature of operations for tax purposes.