What to put on the invoice
Specify the service period, project code and billing method. Separate facilitation, preparation and reimbursable expenses if the agreement prices them separately.
Example line items
The following amounts are fictional examples, before tax or discounts. Use your own agreed prices.
September strategy retainer | 1 × 1,200 Additional workshop, approved scope | 3 hours × 100
A practical document sequence
Confirm retainer terms before the period starts. Track overage separately, reference the purchase order on the invoice and reconcile deposits or previous payments.
A mistake to avoid
A retainer is not automatically a fixed number of billable hours. Make rollover, unused time and overage terms explicit in the agreement.