Agents can pay for their own campaigns from a personal billing account.
If you're an admin building a campaign for an agent and they don't show up under Invoice to user, it's one of two things. They haven't set up a personal billing account yet, or they haven't ticked Allow admins to create and invoice campaigns on my behalf.
You'll only see Invoice to user if your office pays per campaign.
✅ How to fix it:
Ask the agent to click their name at the bottom of the sidebar, pick Account, then open the Personal billing tab.
If they see Set up a personal billing account, they press that first and follow the steps.
Tick Allow admins to create and invoice campaigns on my behalf. This box only shows once their personal billing account is set up. Without it, they won't appear under Invoice to user.
Check they've got a card marked Default. No card yet? Press Add a personal payment method (or Add one). If the card form shows Allow workspace admins access?, tick it. If there's a card but it isn't marked Default, open its menu and pick Make Default.
When you build the campaign, pick the agent under Invoice to user.
Agent hasn't added a card yet? You don't have to wait. Build the campaign now and it stays a draft. You'll see Selected billing user has no default payment method until they add one. Once they do, publish as normal. More in Can I build a campaign before adding a payment method?