This endpoint is used for transmitting usage measurement events to either a designated customer or a specific subscription.

Send usage event

The code that identifies a targeted billable metric. It is essential that this code matches the `code` property of one of your active billable metrics. If the provided code does not correspond to any active billable metric, it will be ignored during the process.

The unique identifier of the subscription in your application. This field is mandatory in order to link events to the correct customer subscription.

The precise total amount in cents with precision used by the `dynamic` pricing model to compute the usage amount.

This field represents additional properties associated with the event, which are utilized in the calculation of the final fee. This object becomes mandatory when the targeted billable metric employs a `sum_agg`, `max_agg`, or `unique_count_agg` aggregation method. However, when using a simple `count_agg`, this object is not required.

This field captures the Unix timestamp in seconds indicating the occurrence of the event in Coordinated Universal Time (UTC).
If this timestamp is not provided, the API will automatically set it to the time of event reception.
You can also provide miliseconds precision by appending decimals to the timestamp.


This field represents a unique identifier for the event.
It is crucial for ensuring idempotency, meaning that each event can be uniquely identified and processed without causing any unintended side effects.

WARNING: If the Lago organization is configured to use the new Clickhouse-based event pipeline (designed for high-volume processing), the idempotency logic is handled differently.
Event uniqueness is maintained with both `transaction_id` and `timestamp` fields.
If a new event arrives with identical values for these two fields as an existing event, the new one will overwrite the previous event rather than being rejected.


The creation date of the event's record in the Lago application, presented in the ISO 8601 datetime format, specifically in Coordinated Universal Time (UTC). It provides the precise timestamp of when the event's record was created within the Lago application

The unique identifier of the subscription within your application. It is a mandatory field when the customer possesses multiple subscriptions or when the `external_customer_id` is not provided.

Unique identifier assigned to the customer within the Lago application. This ID is exclusively created by Lago and serves as a unique identifier for the customer's record within the Lago system

Unique identifier assigned to the event within the Lago application. This ID is exclusively created by Lago and serves as a unique identifier for the event's record within the Lago system

Unique identifier assigned to the subscription within the Lago application. This ID is exclusively created by Lago and serves as a unique identifier for the subscription's record within the Lago system

The precise total amount that was sent in the event payload. This filed is used by the `dynamic` pricing model.

The `operation_type` field is only necessary when adding or removing a specific unit when the targeted billable metric adopts a `unique_count_agg` aggregation method. In other cases, the `operation_type` field is not required. The valid values for the `operation_type` field are `add` or `remove`, which indicate whether the unit is being added or removed from the unique count aggregation, respectively.

This field captures the Unix timestamp in seconds indicating the occurrence of the event in Coordinated Universal Time (UTC). If this timestamp is not provided, the API will automatically set it to the time of event reception.

This field represents a unique identifier for the event. It is crucial for ensuring idempotency, meaning that each event can be uniquely identified and processed without causing any unintended side effects.

bearerAuth

Send usage events

Lago

Lago is an open-source software for metering and usage-based billing. It's the best alternative to Chargebee, Recurly or Stripe Billing for companies that need to handle complex billing logic.

Welcome to Lago

Why billing is a nightmare

Lago Cloud is the fully hosted version of our open-source billing API.

Lago Cloud

Coupons allow you to offer discounts to your customers. When you apply a coupon to a customer,  its value will be deducted from their next subscription invoice(s).

Coupons

Credit notes

Model your revenue-sharing structure within Lago.

Revenue share

Webhooks

Send automatic emails when issuing an invoice or any billing documents.

Emails

Entitlements

This step-by-step integration guide will help you get started with Lago.

Integration testing

Lago OpenAPI

Migration to v1.25.0

Migration to v1.20.0

Migration to v1.2.0

Lago API allows your application to push customer information and metrics (events) from your application to the billing application.

Getting started

Find all Lago integrations with third-party tools—whether for payment providers, alerting systems, or data integrations. Note that some integrations are native and actively maintained by Lago, while others are community-developed and come with limited support.

Introduction

Replicate these popular B2B pricing templates to kickstart your journey with Lago.

Replicate Mistral's per-token pricing model with Lago.

Clone Mistral pricing

Replicate OpenAI's per-token pricing model with Lago.

Clone OpenAI pricing

Replicate Segment's hybrid pricing model with Lago.

Clone Segment pricing

Replicate Stripe's per-transaction pricing model with Lago.

Clone Stripe pricing

Replicate Algolia's pay-as-you-go pricing model with Lago.

Clone Algolia pricing

Replicate BigQuery's pay-as-you-go pricing model and offer free upfront credits with Lago.

Clone Google BigQuery pricing

Replicate Notion's per-seat pricing model with Lago.

Clone Notion pricing

About Lago

About the software

Community

Deployment

General

Pricing

Product features

Product updates

Deploy Lago seamlessly on your infrastructure, compatible with both free and premium editions.

Overview

Docker is the easiest way to get started with the self-hosted version of Lago.

Docker

Tracking & Analytics

Versions update

Useful commands

Billable metrics define how incoming events are aggregated in order to measure consumption.

Create billable metrics

Recurring vs metered

For more advanced calculations, you can use SQL custom expressions. These expressions are helpful when the aggregation results for a billable metric require complex calculations.

SQL Expressions

Lago aggregates your events in real time. You can add rounding rules to the final result.

Rounding

When setting up your pricing, you may want to filters events according to their property. To do so, you can create filters for your billable metric.

Filters

Delete billable metrics

If Billable metrics are made to measure customer usage, Plans are made to apply prices to this usage.

The plan model defines when and how much a customer is charged.

Plan model

Commitments

Progressive billing, also known as threshold billing, automatically triggers an invoice when a customer's cumulative usage reaches predefined thresholds. This method ensures that customers cannot exceed certain usage limits without ensuring payment is received, reducing the risk of unpaid services or fraud.

Progressive billing

Customer management

Customer metadata

Invoice a customer

The customer portal

A subscription is created when a plan is assigned to a customer.  You can assign a plan to a customer at any time (i.e. when the customer record is created or later on).

Assign a plan to a customer

Customers have the flexibility to easily upgrade or downgrade their plan at any given moment.

Upgrades and downgrades

You can edit a subscription at any time, whether it's active or pending.

Edit a subscription

You can terminate a subscription at any time, whether it's active or pending.

Terminate a subscription

Add-ons are a useful feature that allows you to add a fixed charge that is not recurring to one-off invoices.  This can be used to apply one-time fees such as a setup fee, one-time payment, or customer success fee.

Create add-ons

One-off invoices allow you to bill immediately one or several add-ons to a customer.  This guide will show you how to create a one-off invoice for a specific customer using the add-ons.

Issue one-off invoices

This guide explains how Lago ingests usage-based events coming from your application.

Ingesting usage

By ingesting events, you can see them flowing in the Lago application by using the events list. It allows you to take a deeper look at ingested events and detect possible warnings.

Events list

Learn how to retrieve usage data for both current and past billing periods.

Retrieving usage

Here is a list of sources you can use to ingest usage data. Some of these sources are capable of handling up to 15,000 events per second with default settings.

Metering ingestion sources

Lago automatically generates invoices for each customer according to the plan model.

Fees

When generating invoices, you may need to apply vat or other taxes. By creating taxes and applying them to the organization or/and customers,  their invoices will be directly affected.

Taxes

Grace period

Net payment term

Download invoices

Invoice metadata

With Lago, you can preview invoices even if the customer doesn't exist yet or for an active subscription, allowing you to generate dry-run invoices or estimate potential bills.

Preview an invoice

Void invoices

Lago enables you to filter invoices and export them as a simple or advanced CSV file, tailored to your needs.

Export invoices

Connect Lago to any payment providers by using native integrations or webhook messages.

Lago's native integration with Stripe allows you to collect payments automatically when new invoices are generated.

Stripe integration

Lago's native integration with Adyen allows you to collect payments automatically when new invoices are generated.

Adyen integration

Make your users pay Lago invoices with Cashfree Payments, India's leading payments and API banking company.

Cashfree Integration

Lago's native integration with GoCardless allows you to collect payments via direct debit.

GoCardless integration

Payment retries

Lago automatically generates payment receipts for each payment processed, whether manual or through payment provider integrations.

Payment receipts

Dunning refers to the process of communicating with customers to remind them of overdue invoices and attempt to recover the outstanding amounts.

Manual dunning

Automate customer communications to remind them of overdue invoices and recover outstanding balances through targeted dunning campaigns.

Automatic dunning

Since usage-based charges can be calculated at the end of the billing period, you often need to wait to collect payments. With prepaid credits, you can now unlock recurring revenue opportunities for pay-as-you-go pricing models.

Add and void credits, to the customer's wallet.

Top-up and void credits

Overdue invoices

Gross revenue

Monthly Recurring Revenue (MRR)

Invoice collection

API Keys

RBAC - Role Base Access Control

Single Sign-On (SSO)

SOC 2 Type 2

This object represents an add-on, a one-time fee that can be applied on one-off invoices.

The add-on object

This endpoint is used to create an add-on that can be then attached to a one-off invoice.

Create an add-on

This endpoint is used to update an existing add-on.

Update an add-on

This endpoint is used to delete an existing add-on.

Delete an add-on

This endpoint is used to retrieve a specific add-on.

Retrieve an add-on

This endpoint is used to list all existing add-ons.

List all add-ons

Gross revenue is the sum of monthly `finalized` invoice payments and fees paid in advance that are not invoiceable. This total is calculated after deducting taxes and discounts.

Retrieve gross revenue

Retrieve MRR (monthly recurring revenue)

Reports a monthly analysis focused on the revenue generated from all usage-based fees. It exclusively accounts for revenue that has been formally invoiced. Importantly, this report does not include revenue related to the usage in the current billing period, limiting its scope to previously invoiced amounts.

Retrieve invoiced usage

Represents a monthly aggregation, detailing both the total count and the cumulative amount of invoices that have been marked as `finalized`. This report sorts invoices categorically based on their `payment_status`.

Retrieve invoice collection

Overdue balance is the total amount associated with overdue invoices (invoices with pending or failed payments which are past their due dates).

Retrieve overdue balance

This object represents a billable metric used to define how incoming events are aggregated in order to measure consumption.

The billable metric object

This endpoint creates a new billable metric representing a pricing component of your application.

Create a billable metric

This endpoint updates an existing billable metric representing a pricing component of your application.

Update a billable metric

This endpoint deletes an existing billable metric representing a pricing component of your application.

Delete a billable metric

This endpoint retrieves an existing billable metric that represents a pricing component of your application. The billable metric is identified by its unique code.

Retrieve a billable metric

This endpoint retrieves all existing billable metrics that represent pricing components of your application.

List all billable metrics

List all billable metric groups

This object represents a coupon used to applies discount on customer next invoices. This coupon can be applied to a customer with overriden values.

The coupon object

This endpoint is used to create a coupon that can be then attached to a customer to create a discount.

Create a coupon

This endpoint is used to update a coupon that can be then attached to a customer to create a discount.

Update a coupon

This endpoint is used to delete a coupon.

Delete a coupon

This endpoint is used to retrieve a specific coupon.

Retrieve a coupon

This endpoint is used to list all existing coupons.

API Reference

Send usage event

Authorizations

Body

Response