How to Calculate GST based on Sub Total

Greeting all
I wanted to calculate the GST based on the subtotal . It should be 5% of the subtotal if it is less than Rs 1,000; otherwise, it should be 12% of the total billing amount. How you use OpenCart to accomplish this.
With regards
Swathi

Is the "total billing amount" different from the sub-total?

You could use Total-Based Fee/Discount for this. You'd set it up like this:

------------------------------------------------------------------------------
CHARGE #1
Title: GST
Sort Order: 1
Charge Field: 0-1000 = 5%, 1000-99999 = 12%
------------------------------------------------------------------------------

By default, any total-based calculation will use the cart sub-total for the total value. To change this, you need to apply a "Total Value" rule, like this:

Rule: Total Value = Total

That will change it so any total-based calculations use the full total at the point of the extension, instead of the cart sub-total. Feel free to take a look at the screenshots and demo site, and if you're interested let me know at www.getclearthinking.com/contact if you have any questions.