There are returns to be filed every month.
Important is that Your invoice should contain GSTIN /HSN/ SAC CODE/ details of SGST/CGST/IGST amounts.State Codes of both Service Provider and Reciever is to be provided.
Suggest Pls avails guidance From CA.TO know more in details
29th July 2017 From India, Vadodara
If at all your business turnover is exceeding 20,00,000/- per annum then GST is mandatory. If it is less then it is optional & it is your wish to opt for GST or Not. If less than the limit you can even plan for Compound GST
For invoice you no need to have any standard format but the minimum base requirements need to be captured in invoice such as bot yours as well as your customers GSTIN & HSN/SAC Code, SGST,CGST & IGST numbers as well as the rate of tax
No need to have any software & you can design the same either in word or excel. Excel format would be better as you can assign the calculations
29th July 2017 From India, Bangalore