There are interim tax returns for;
1. Corporate Income Tax(Must/the end of August for December closing company if there was no tax to pay or less payment), usually a lot of entity used to pay the half of the amount which they calculated on the last fiscal year at the end of March without a filing.
But if it's business was not going well during the first half of year, they need to file to pay less or not to pay by the end of August.
2. VAT(April 25 and Oct.25 for Sole Proprietor-ship owner if needed to pay more or less than the half amount paid before term).
Usually a sole-proprietor need to pay the half of the amount paid on the July 25 according to the tax bill issued by the NTS, but need to file to pay less if it's reduced more than 20% less comparing last half.
3. Individual Income Tax(by the end of November, if needed to pay or less than you paid on the last May).
These interim tax also will be charged by NTS by a tax bill.
Any questions, or comments, please feel free to contact me to firstname.lastname@example.org