Under GST you can claim the taxes you have paid on inputs (purchases) from the taxes you are supposed to pay on output(sales).
To be able to claim this benefit, you must meet the following conditions –
1. Payment the supplier within 180 days from issue of invoice
2. Inputs and capital goods should not be used for personal purposes
3. Inputs and capital goods should not be used for providing exempt supplies
If you do not meet these conditions, you are not allowed to claim input credit of the taxes paid on inputs. However, these purchases automatically reflect in your GSTR-2A and therefore you will have to do a reversal of input tax credit on these purchases while filing your GSTR-2.