Citizen Calculator GST, developed by BrownDwarf, is a free Android application that serves as a business calculator with check and correct functionalities. It is referred to as a "Check and Correct calculator" and has Indian number system comma placements to show place values. With its retro Citizen calculator looks, it provides a unique experience to its users.

The app comes with several features, including the ability to swipe to view calculation list or options, save and load calculations, share calculations, and a GST calculator. It also has an option to remove the GST calculator, and all existing themes have a GST tax calculator. Recently, the app added an auto replay function that redefines the way check and correct Citizen calculator used to work. Additionally, the Citizen calculator now comes with material design themes for people who want a more modern look, while preserving the old retro look with a modern touch.

Overall, Citizen Calculator GST is a useful tool for businesses and individuals who require a calculator with check and correct functionalities, and its unique features make it stand out from other business calculators on the market.