How the calculation works on PKR 3,00,000 / month
At 300,000 a month you're into top-tier salary territory, usually C-suite or specialist work, and into the 30% marginal band where almost a third of each extra rupee goes to tax. That's 3,600,000 a year. After the 346,000 fixed amount plus 30% on the income above 3,200,000, your tax is 466,000 a year, or about 38,833 a month. Your effective rate is 12.94%, but the rate on anything extra is now 30%.
That works out to roughly Rs 38,833 a month deducted from your gross, leaving you with Rs 2,61,167 take-home. Your effective tax rate is 12.94%, even though your marginal rate is 30%.
What changes if you're not salaried?
At this income the salaried route is clearly the lighter of the two ordinary options. A non-salaried filer on 3,600,000 a year faces a heavier structure. Registered IT export income at a flat 0.25% is still far lower than both, which is why, at this level, how your income is classified is worth a six-figure sum every year.