Sales tax is fairly complex issue. Requirements and rates vary from country to country and sometimes from state to state.
When an order is being processed on TeachersToTeachers.Net our system currently calculates how much sales tax should be charged on the item depending on the buyers location.
We do not retain any of this sales tax. If it is charged, it will be available as part of your earnings.
Recently (2018), ‘remote seller sales tax’ has been adopted by some countries in some regions. This law requires that if a large number of your purchases come from buyers in a certain region then you will have to collect the sales tax and pay tax to the appropriate authority in that region. However, clearly “a large number” needs to be defined and this also varies from place to place. As an author, initially your sales will be below the threshold for this tax and may never be applicable. If you start to sell around 300 individual resources into a single region in a year, then you should check with a tax specialist in your country of residence.
Income tax is of course a completely separate issue from sales tax. What you earn on TeachersToTeachers.Net is however part of your annual income and you need to declare these earnings on your annual tax return to the tax authority in your country of residence.