Income for individual in economics is calculated after the tax or before the tax ? Becasue while generating budget constraints if say below 10 lakh there no tax , between 10 to 15 lakh there is 10% tax then person earning 11 lakh actually earn 9.9 lakh ,then how to draw budget constraint in such cases of net income ?

Also if one can show how budget constraint in differnt tax slab looks like it would be really good.