Formal Start Dates

After I’d registered as an auto-entrepreneur on 27/12/20, a few days later, downloaded and printed a unique form pre-filled for me in titled ‘DECLARATION DE DEBUT D’ACTIVITE’ , DATE DE DEBUT D’ACTIVITE 27/12/2020 reçue le 30/12/2020.  I signed this at the time, but have not sent it anywhere yet. 

A) Should I send (email/post) this 2 page landscape orange form, signed back to my local URSSAF?
NB: On this form the social security number is only zeros.

So, I thought I had created my AE URSSAF online account on the 27 December 2020, only to discover there seems to be another account you need to create from that website for registering online quarterly earnings.  I only did that on the 25/02/2021, and got an electronic message coming up saying ‘Debut d’Activities’ as of that date, but perhaps that’s just the date for declaring online….  I invoiced in January 2021, and had assumed I was all registered.

B)    Because I did invoice and get paid in January 2021, am I alright regarding the start of the business being before the turn of the year,
or should I try to correspond with the URSSAF office to clarify re the 25/02/21 date? (NB: I also received a postal letter saying I was affiliated to Ameli & URSSAF & CNAV (L’Assurance Retraite) as of 27/12/20.)

C)  Can you also tell me if opting for the Micro-Social Regime within the Regime Fiscal Micro (Micro Tax regime) is the same as Impôts Liberatoire, that you refer to in your video?