You do not need to sign up to invoice. The anonymous builder lets you create a full invoice, share it, and save it to an account afterward if you want.
Step 1: Start a blank invoice
On the homepage, click Create a blank invoice (or Create an invoice), which opens the builder at /new.
Step 2: Add your sender details
Since there is no profile to pull from, fill in your own sender and payment details along with the recipient, dates, currency, and line items.
Step 3: Create and get the link
Click Create & get share link. This saves the invoice in your browser and opens the saved-invoice page.
Step 4: Share with your client
On that page, use the Copy button under the share section. Anyone with the link can view and interact with the invoice, no account needed on their end.
Step 5: Save it to an account (optional)
To access the invoice from any device and keep your profile and customers, click Save to an account on the same page.