The purpose of this study is to analyze the effects of tax audit probability, penalties on tax practitioners, and client attitudes on tax practitioners' decision-making in situations where tax law provisions are ambiguous. To achieve this objective, a hypothetical case involving ambiguous tax law provisions was developed, and data were collected through questionnaire surveys administered to actual tax practitioners. The data analysis results showed that tax audit probability and penalties on tax practitioners—tools available to tax authorities as sanctions against tax practitioners—did not have statistically significant effects on tax practitioners' decision-making. However, the interaction between tax audit probability and penalties did have a statistically significant effect on tax practitioners' decision-making. This result suggests that if tax authorities appropriately utilize penalties on tax practitioners in conjunction with current tax audits, they may be able to induce tax practitioners to file more compliant returns. Client attitudes did not have a statistically significant effect on tax practitioners' decision-making. Beyond these variables, tax practitioners' risk preference attitude was found to have a statistically significant effect on their decision-making. This result indicates that Korean tax practitioners tend to make decisions based on their personal dispositions and convictions rather than external pressures.