The stage column is canal_etapa on the invoice itself. It advances by two triggers.
Automatic advance
A nightly cron checks days-past-due against each stage threshold. Hit the threshold, advance the stage, trigger the playbook for that stage.
Manual advance
Open the invoice → Collections panel → "Advance stage". Use when a customer breaks a promise-to-pay or you want to fast-track escalation.
Hold
Sometimes you negotiate a payment plan offline. Click "Hold" on the invoice; it stays in Collections but stops triggering automation for a configurable window.
Resolve
When the invoice gets paid, it auto-exits Collections. If paid partially, it stays in the current stage with the residual balance.