GST rate & HSN CODE for Electricity chsrges

You can't issue an invoice of electricty to another branch of the company because electricty is good and if you are not supplying such good to your another branch then how you can issue an invoice for that. Also you can't distribute the credit of GST to another branch as a ISD.

Sir, Both companies are in the same building but bill received on our company name, so we have to distribute this expenses, for transferring expenses we have to raise a bill, is it correct?
For billing we need GST rate and HSN code. kindly advise us

Yes you are right for transferring or sharing of expenses you have to generate some document but as per law invoice should be of supply and if there is not any supply how we can generate a Tax invoice.
In this case you have to reverse the proportionate ITC in you GSTR 3B and ask from such person to pay the amount of electricty charges including the Taxes as the expenses paid by you on his behalf.
In this whole thing such third person have to bear the loss of Taxes paid on his proportionate charges.

As per Section Section 15 (2) , it's kind of reimbursement & in GST for reimbursement the the Tax Invoice can be issued.

But there will be no GST applicable as Electricity is exempted by vide Notification 12/2017 CT (r) under S.no.25.

SAC code Is 9969.

Note : Reimbursement on actual basis is exempted , if you are adding any profit on same then it's taxable

Sir can you please explain how as per section 15(2) Rao ji can issue the invoice for reimbursment of expenses because section 15(2) tells about the things which are to be included in value of goods or service supplied. Also they are not falling under the definiation of "Pure agent". Tax invoice is governed by Sec 31 and it clearly specify that R.P "supplying" Taxable goods/Service shall issue the invoice. Now question comes to that wether it is treated as a supply of goods or not because electricty is goods not a service.