Invoice date vs Shipment date

Eajaz Ahmad (Accountant) (131 Points)

05 January 2022  
Respected Sirs & Mams..

Our sale Invoice date is 20th December, 2021..
But the Materials were shipped overseas on 4th January, 2022..

How do I treat the sale..
Shall I show in December 2021 GSTR1 & GSTR3...
OR
JANUARY 2022.

Should I follow Invoice Date or Shipping Bill Date.

Suggestions from experts will help me a lot.
Thanks
Eajaz