Very basic question on gst

The retailer need not bother about the inclusive of all taxes portion. If he had purchased the product for say Rs 40, then he would have paid Rs 4.80 (40*12%) as Input GST . The 12% will be divided by Central and State Government upon agreed terms (not yet fixed).

On sale he will collect Rs 6 (50*12%) This will be output tax payable. As ITC of Rs 4.8 is available the net amount paid to Government is Rs 1.20.

IGST can be set off against all types of GST. CGST and SGST cant be cross set off. Same side set off along with IGST set off is possible.

Hoping it clarifies your doubt.

that means retailer will charge 50 + 6 (GST) Total Rs 56 from the customer???

Yes he will collect Rs 56 from the customer. Out of the 6 Rs he collected as Tax he will only pay Rs 1.2 (6 - 4.8) to Govt.