VAT (Default surcharge)

Kaplan Revision Book FA2019: Knight Ltd., page 193 Task (Extract): Knight Ltd. was late in submitting the following VAT return and in paying the related VAT: Return Period VAT due 3 months ended 31/12/2017 20,000 3 months ended 30/09/2019 30,000 3 months ended 30/6/2020 21,000 All of the company's other VAT return have been submitted on time, and the related VAT liabilities have been püaid on time. Answer (which I understand) The late payment for the quarter ended 30/09/2019 ---> a surcharge liability notice up to 30/9/2020. The late payment for the quarter ended 30/06/2020 ---> 2%*21,000 = 420 and surcharge period extended to 30/6/2021. Answer (which I don't understand, can you please explain this sentence below?): The late submission for the quarter ended 31/12/2017 IS IRRELEVANT, as it was followed by the SUBMISSION of FOUR (?) consecutive VAT returns on time.