Tax evasion is common in our country where people dislike paying tax due to the various factors. The government of Tanzania has focusing itself on raising revenue from various limited number of resource, TRA was formed as government agency charge with collection of revenue but still the number of those who are paying tax are few. Tanzania one of the important areas where tax evasion has been reported is customs duties. Despite its importance, limited scientific research has been undertaken the assessment of tax evasion practices in Tanzania. This study aimed to assess the extent factors that influence tax evasion a case of TRA Mwanza. Specifically, the study sought to assess the accountability on tax collection; ascertain the influence of corruption on tax collection; discern the impact of staff ethics on The study was conducted through a descriptive design using a cross sectional survey within TRA Mwanza. The study employed purposive sampling to select the sample and sample elements. This resulted to a sample size of 80 staff. A structured questionnaire as a data collection instrument was used. The field data was statistically analyzed using descriptive statistics and narrative summary analyses. Findings indicate that accountability has a significant impact to TRA, lake of knowledge to taxpayer, corruption among those who are responsible, high rate of tax which causes some of them to evade tax.