"GST - An initiative to create a unified national market," the finance ministry said in a tweet, attaching the video.
In the video, Mr Bachchan explains GST as an unifying force just like the three colours in the national flag. GST is an initiative to create 'one nation, one tax, one market', he says.
The rollout of the biggest tax overhaul since independece entered its final phase. Olympic-medal winning badminton player PV Sindhu was previously the GST ambassador.
GST will simplify a web of taxes, regulations and border levies by subsuming an array of central and state levies including excise duty, service tax and VAT. It is being dubbed as the most significant economic reform since BJP government came to power in 2014 and is expected to add as much as 2 percentage points to the GDP growth rate.
GST also represents an unprecedented exercise in fiscal federalism. The GST Council, that brings together the central and state governments, has met 17 times to thrash out how the tax will work.