Why is the minimum commitment not appearing as a line item on an invoice?

A minimum commitment charge is intentionally left off an invoice when the customer's prorated minimum commitment for that billing period is less than their total usage charges. The customer has already exceeded the minimum through usage, so there's nothing left to bill for it.

How it works

The minimum commitment is prorated based on the number of days in the subscription for that period. Lago compares that prorated amount to the customer's total usage charges; if the prorated minimum is the smaller of the two, the minimum commitment line item is suppressed. This is expected platform behavior, not a bug.

How to confirm the cause

1. Pull the invoice.created webhook payload for the invoice and note the subscription_at date and total_amount_cents (the invoice's total charges).

2. Check the plan configuration for the customer's minimum commitment amount, for example $500/month.

3. Calculate the prorated minimum commitment: minimum commitment divided by total days in the billing period, multiplied by subscription days used. For example, a subscription_at date of February 20 gives about 9 subscription days in a 28-day February: $500 / 28 x 9 is approximately $160.71.

4. Compare that prorated minimum to total_amount_cents. If the prorated minimum is lower, the minimum commitment line item won't appear on the invoice, and no action is needed.

This article reflects guidance drawn from customer case resolutions. It is not officially supported documentation and may not apply to all situations.