When so many persons are still working on annual return for 2017-18 it is nice to note that you have filed returns and also ready to file return for the second year of GST. Till the time the return for 2018-19 is enabled in GSTN you may do the following activities.
1. Carry out GSTR 2A reconciliation
2. Communicate the discrepancies to your vendor.
3. Follow up with them if they have rectified the errors reported by you in his return.
4. In this process you will identify the unutilised input tax credit which you can claim before 30th September 2019.
5. Similarly also check the outward supplies reported by you and if any correction found out or any tax is missed to be paid then pay it with interest.
6. Send an email communication to all your customers asking them to check their GSTR 2A. So that they can report to you before September and you can rectify them before time.
7. On the basis of 2017-18 audit you must have come to know the errors committed inadvertently or any process needs change. Then all of those things you can take care for this year.
8. Any other activity which you come across while doing the above activity must be done proactively. In GST both supplier and buyer are like left and right hand.