In Marg, we have an option to manage Sale price increase/decrease according to the customer requirement (like: Ravi is a Buyer and Kapil is a Seller. Before GST, Kapil sell goods to Ravi for Rs. 110 but after GST implementation, Kapil sells the same goods to Ravi for Rs. 150 but goods MRP is 160. Ravi has not taken goods at the new price with less Margin (the good thing is that Kapil is using MargERP9+ where it has the option of rate customize for their customers.) So, Kapil sell the goods to Ravi on Average Rate

Set Average Rate 

Go to Master > Ease Of GST Adoption > import Hsn/Sac/%Gst rate from excel > Here option show Rate+- > You can press F11 (For calculate average tax% ) > then feed that average tax percentrage in Rate+- > Then save in both>set effect of this rate  in purchase/sale/cost/sale+purchase+cost > Save