Retainers & installment billing

Retainer billing

For clients on a fixed monthly retainer, Opterflow can auto-generate an invoice at the start of each billing cycle.

1. Go to Clients → [client] → Billing
2. Set Billing type to Retainer
3. Set the monthly amount and billing day
4. Toggle Auto-generate invoice on

Each billing cycle an invoice is created in Draft state — review and send it, or enable auto-send.

Installment billing

For large project fees, split the total into milestones:

1. Create a new invoice
2. Enable Split into installments
3. Set the number of installments and due dates for each

Opterflow creates a linked installment series. When each is paid, the project balance updates automatically.

Quarterly & annual retainers

Set the billing frequency to Quarterly or Annual when creating the retainer. Opterflow normalises the value to MRR/ARR in the Clients dashboard for consistent revenue reporting.

Pausing a retainer

Go to Clients → [client] → Billing → Pause. No invoices are generated while paused. Unpause any time to resume on the next cycle.