Filing of return by supplier for claiming ITC during FY 2018-19 - Goods and Services Tax - GST

Dear Experts Few of my clients have received GST notices disputing ITC for FY 2018-19 on the ground that their suppliers have filed their returns after the Cut-Off date for FY 2018-19 ie. 20 Oct 2019 ITC; though the client has taken ITC prior to 20 Oct 2019. No section is mentioned in the SCN As per my understanding of section 16(4) provides time limit for availment of credit by recipient and has no relevance with filing of return by supplier. In fact there was no condition for FY 2018-19 regarding the supplier's return filing. Please confirm