After verifying your email, signup asks how you will use swipesign and which country you are in.

| For | |
|---|---|
| Private use | Yourself or your household: personal contracts, agreements, leases |
| Company use | A business: contracts, NDAs, employment, board resolutions |
The screen tells you it helps us set up the right workspace, and that you can change it later. So it is a starting point, not a commitment.
Which to pick
Choose Company use if you are signing on behalf of a business, will need colleagues in the workspace, or want invoices in the company name. That covers most people reading this.
Choose Private use if it is genuinely just you and your own paperwork.
Company details
Choosing Company use reveals a field for your VAT ID, so you can enter it here and have it on your invoices from the start.
You do not have to. There is no separate company-details step in signup, and everything billing-related, billing name, country and VAT ID, also lives on the Invoices page and can be filled in or corrected at any point. Doing it before your first invoice is issued is soon enough.