Let's try to understand how to online and offline quarterly TDS return via software. So, SAG Infotech provides to the taxpayers help India's most popular Gen TDS/TCS return filing software that is government authorized since 2012 in the finance industry. Here we have described a step-by-step process like taxpayers can fill the e-TDS and e-TCS form in a prescribed format, which is on the TIN NSDL website, the second step is users can assemble the data for TDS/TCS in clean text ASCll format and easily prepare the file with a. txt extension and much more.