While an invoice is in draft status, you can:
  • Add usage records by sending event with a valid timestamp within the billing period
  • Edit specific fees (adjusting total amount or unit count)
  • Apply coupons to the customer’s account
  • Add credits to the customer’s wallet or credit note wallet

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Add fees to draft invoice

Since Lago does not generate fees for charges with 0 units, some may not appear in the draft invoice by default. You can add them either by sending usage records or manually through the Dashboard:
  1. Open the draft invoice details;
  2. Click Add a fee (if applicable);
  3. Select the charge and filters;
  4. Adjust the display name (optional);
  5. Choose between Total amount or Total unit;
  6. Input your values — note that Total amount overwrites the original fee;
  7. If using Total unit, Lago recalculates the fee automatically.
Manual fee editing is only available via the Dashboard.

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Edit a specific fee

If a fee has already been added to the draft invoice, you can edit it from the Dashboard:
  1. Open the draft invoice details;
  2. Click the three-dot icon next to the fee;
  3. Adjust the display name (optional);
  4. Choose Total amount or Total unit;
  5. Input new values — same recalculation logic applies as above.
Manual fee editing is only available via the Dashboard.

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Add usage records

In order to add usage to an invoice that is in draft status, the timestamp of the events must be within the billing period. Consider the following example:
Billing period: January 1 – January 31 Grace period: 3 days Today: February 2 A draft invoice was generated on February 1. To send additional usage for this invoice, the event timestamps must fall between January 1st and 31st. ✅ Usage event on January 11 (timestamp: 1673457300) → included ❌ Usage event on February 2 (timestamp: 1675354500) → excluded (will be part of next invoice)
After sending new events, refresh the relevant draft invoice to see the events taken into account. When the grace period ends, invoices in draft status are automatically finalized. Alternatively, you can finalize them manually via the UI or API. Once finalized, invoices are locked and trigger the invoice.created webhook.

Draft invoice in the Lago app

Coupons and credits added during the grace period won’t appear on draft invoices, but they will be automatically applied to the next finalized invoice.