Here is how the presumptive taxation scheme can be opted on Quicko to file ITR4:
1. Add business income/professional income
2. Fill in details: name of business, description, category and subcategory and click on save and continue
3. You will see a page indicating 'Do you want to opt for the Presumptive Taxation Scheme u/s 44AD' and you can click on yes
4. Enter the revenue and profit figures (digitally and via cash) and your taxable income will be calculated as per the presumptive taxation rules.