Accounting of 2017-18 gst input in the current year

If those omitted bills can't able to reflect in GSTR 2A in future, you should show those GST paid as expense.. Not to be shown in Current Assets

you can avail itc in respect bills from 1-7-2017 to 31-3-2018 by last in sep 2018 return gst-3b after sep you cant take itc and entries for that itc is that you debit input tax and credit respective expense related to your itc as when you passed entry in previous year you added itc in you expense hence you expense debited by excess amount so now you reduce it to increase itc in current fy

Hi , Previous year , you have considered more expense. So Debit the GST Input Credit and reduce the expense.
for example
Dr Igst
Cr XXX

The time limit for considering the input is b4 one year or filing of Annual Return , whichever is earlier.