Can we take GST input, whose GST Return still pending

Yes, you can generally claim GST input tax credit (ITC) based on an invoice even if your supplier's GST return is pending. However, it's crucial to ensure that the supplier eventually files their return and pays the GST. For periods affected by lockdown, Rule 36(4) allows consolidated ITC claims, but for other periods, you must adhere to the specific conditions of Rule 36(4) when claiming ITC.