Inter state sale under gst

we are already registered in Maharashtra under GST.

just we need to add IGST instead of CGST & SGST?

but IGST liability can be settled against CGST & SGST input?

yes & it is not convenient to purchase the material from Maharashtra & incur high cost towards transportation up to M.P.

instead if we take registration in M.P. we can purchase & make sale from that state itself.

in tally can i maintain both state purchase under same company?

bank is the same for both state but gst registration number will be different 

I would suggest to open a separate bank account in M.P for sake of convenience and maintain project wise accounts and finally consolidate for IT purpose at the end of FY.

should  i maintain cost center wise accounting in a single company or create different company ?

but if multiple gst registration numbers are there for same company i wont be able to file gst returns from tally itself i think

if we want to transfer goods (that is left at site) from our site in Maharashtra to the other  site (different branch having different GSTIN) in M.P. i.e.interstate transfer of goods, we need to issue e-way bill? actually multiple goods are there that we had purchased from other suppliers for construction which need to be transferred to new site in M.P. for construction only.so how to determine the value of consignment? while creating e-way bill should i register with GSTIN of Maharahtra or M.P.? should i treat it as sell & pay the gst? 

so under gst it will be like sale from  Maharashtra to M.P. with IGST 

& can i take credit of the same in M.P.?

in tax invoice i should mention same company name with M.P. GSTIN? means seller name & buyer name will be same in invoice but different GSTIN & different addresses