Yes - adding a social security number is not mandatory when creating a new customer in the CRM.
However, without a stored social security number in the CRM (in the customer's details), you will not be able to utilize all features in Linear. Without a SSN, it is not possible to send documents for electronic signature to the customer from Linear, nor can a capital gains tax declaration be made on their behalf, or start a DIAS trade.
Please note that if you do not know the customer's SSN when creating them in the CRM, you can later edit the customer's information and update the missing information:
If a customer requests that their social security number not be stored in the CRM, contracts must be signed by hand and the capital gains tax declaration must be made via the Tax Administration's website.