When creating a new Stripe Express account there are 2 business types you can choose from.
1. Non-Profit
If you are a registered non-profit, you will need to provide your SSN/SIN when creating the account so Stripe is able to verify who you are.
Proof of address document
Your registered business address
Some personal information such as email, address and date of birth
Your bank account you want to receive payouts to
2. For Profit with Business ID
You will need to provide your SSN/SIN when creating the account so Stripe is able to verify who your are.
Your registered business address
Some personal information such as email, address and date of birth
Your bank account you want to receive payouts to
Photo identification
Proof of address document
If you can't provide some of those documents during account creation, you are able to submit it at a later date by logging in to Stripe and going to your settings and clicking on Account Status
If you have more questions regarding why this is required, please check out this Stripe Help Article