Queries regarding gst in f.y. 17-18

Yes you can... however you need to reverse ITC if payment not made within 6 months.

Txs. Sir...... my another queries regarding this......, whether income Tax Department send legal notice for not booked purchase in 2017-18 ?? .... ..

They won't as you omitted to include expense in your books and paid tax on higher income. Now, you can book such expense in current financial year & claim GST, subject to conditions prescribed in GST Acts, but you can't use such expense for reducing your tax liability, in other words, prior period expenses are not allowed as per Income Tax Act.

TXS. SIR.... ....