If your workspace is on invoice billing, you can add multiple seats and receive an invoice for them.
Go to Settings → Billing.
Select ⋯ next to your plan and choose Add seats by invoice.
Enter the number of additional seats. The total is prorated for the remainder of your current billing period.
Select Send invoice.
The seats are added to your plan right away, so you can add members immediately.
The invoice is emailed to your billing email and appears under Invoices in Settings → Billing, marked Unpaid until it’s paid. It’s due within 30 days.
Only the billing owner can add seats by invoice, and the option is available once you’ve switched to invoice billing (see Switch to invoice billing). If your payment is past due, pay the outstanding invoice first.