Following up on late invoices is a chore that never quite ends, yet it still asks for good judgment. Most of it is easy: a bill is a few days overdue, you send a friendly nudge, the money arrives. But when to write, how firm to sound and when to escalate all depend on how late the bill is and how big. And a few accounts are delicate enough that no automatic email should leave until someone has checked it.

So an agent on Machine handles the follow-ups for us, once a day. Here's how we collect what we're owed, including what it's connected to and the rails that keep it safe.

The problem

Money owed to you slips through when nobody has a spare hour to go down the list each day. An invoice is a week late, then a fortnight, and the note that should have gone out on the first day just doesn't. Bills that deserve a sterner message get the same bland email as ones that are barely overdue. Meanwhile the delicate cases, like a big balance, a line the customer disputes or an account on its way to legal, are chased exactly like everything else.

The usual answers only go part of the way. Stripe's own reminders run on a set schedule and ignore how large the balance is or what's going on with the account. A spreadsheet plus a calendar alert only works if somebody actually sits down with it. And a one-size automation emails everyone the same thing, with no way to hold back the risky ones.

What we built

A timer on Machine wakes an agent each morning. It opens a session: a fresh cloud computer (a sandbox) used only for that run, with narrow access to Stripe, our email and the accounting ledger. The agent finds every invoice that's late or about to be. For each one it picks the reminder that fits how overdue and how large the balance is, sends it and records the contact. When payment comes in, it reconciles the invoice. Anything delicate pauses for a person to approve before it goes out.

How it works

The pattern

A daily cron opens a session with narrow connectors into Stripe, email and the ledger, and your collections rules live in skills and memory. The agent mostly reads, delicate accounts wait for a person, and each contact is recorded.

Guardrails

This agent emails customers in our name and changes invoice status, so its access is narrow and fenced in:

• Isolation. Each run gets its own sandbox for that one task. The session reads Stripe and the ledger and may send only the reminders and status notes it has been scoped to. Nothing else leaves it.
• Scoped secrets. The Stripe, email and ledger credentials are stored encrypted in the Secrets Manager, delivered into the sandbox when the run starts, and only handed to the agents you grant them to.
• Human approval gate. A big balance, a disputed invoice or an account on its way to legal pauses until a person approves, before any email is sent.
• Everything is code. The agent's setup, skills and permissions for each system are files in your repo. They're versioned, and you change them through a reviewed change request, not a dashboard toggle.

The outcome

Late invoices now get the right nudge on the right day, every contact is on record, and each payment is reconciled as soon as it arrives. Everyday follow-ups take care of themselves, the delicate accounts wait for a person, and collecting what you're owed no longer hangs on someone carving out an hour for it.