Start a subscription checkout
curl --request POST \
--url https://api.newinvoice.dev/v1/billing/checkout_sessions \
--header 'Authorization: Bearer <token>' \
--header 'Content-Type: application/json' \
--data '
{
"plan": "starter",
"success_url": "https://example.com/webhooks/invoice",
"cancel_url": "https://example.com/webhooks/invoice"
}
'import requests
url = "https://api.newinvoice.dev/v1/billing/checkout_sessions"
payload = {
"plan": "starter",
"success_url": "https://example.com/webhooks/invoice",
"cancel_url": "https://example.com/webhooks/invoice"
}
headers = {
"Authorization": "Bearer <token>",
"Content-Type": "application/json"
}
response = requests.post(url, json=payload, headers=headers)
print(response.text)const options = {
method: 'POST',
headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
body: JSON.stringify({
plan: 'starter',
success_url: 'https://example.com/webhooks/invoice',
cancel_url: 'https://example.com/webhooks/invoice'
})
};
fetch('https://api.newinvoice.dev/v1/billing/checkout_sessions', options)
.then(res => res.json())
.then(res => console.log(res))
.catch(err => console.error(err));<?php
$curl = curl_init();
curl_setopt_array($curl, [
CURLOPT_URL => "https://api.newinvoice.dev/v1/billing/checkout_sessions",
CURLOPT_RETURNTRANSFER => true,
CURLOPT_ENCODING => "",
CURLOPT_MAXREDIRS => 10,
CURLOPT_TIMEOUT => 30,
CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
CURLOPT_CUSTOMREQUEST => "POST",
CURLOPT_POSTFIELDS => json_encode([
'plan' => 'starter',
'success_url' => 'https://example.com/webhooks/invoice',
'cancel_url' => 'https://example.com/webhooks/invoice'
]),
CURLOPT_HTTPHEADER => [
"Authorization: Bearer <token>",
"Content-Type: application/json"
],
]);
$response = curl_exec($curl);
$err = curl_error($curl);
curl_close($curl);
if ($err) {
echo "cURL Error #:" . $err;
} else {
echo $response;
}package main
import (
"fmt"
"strings"
"net/http"
"io"
)
func main() {
url := "https://api.newinvoice.dev/v1/billing/checkout_sessions"
payload := strings.NewReader("{\n \"plan\": \"starter\",\n \"success_url\": \"https://example.com/webhooks/invoice\",\n \"cancel_url\": \"https://example.com/webhooks/invoice\"\n}")
req, _ := http.NewRequest("POST", url, payload)
req.Header.Add("Authorization", "Bearer <token>")
req.Header.Add("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)
defer res.Body.Close()
body, _ := io.ReadAll(res.Body)
fmt.Println(string(body))
}HttpResponse<String> response = Unirest.post("https://api.newinvoice.dev/v1/billing/checkout_sessions")
.header("Authorization", "Bearer <token>")
.header("Content-Type", "application/json")
.body("{\n \"plan\": \"starter\",\n \"success_url\": \"https://example.com/webhooks/invoice\",\n \"cancel_url\": \"https://example.com/webhooks/invoice\"\n}")
.asString();require 'uri'
require 'net/http'
url = URI("https://api.newinvoice.dev/v1/billing/checkout_sessions")
http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true
request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n \"plan\": \"starter\",\n \"success_url\": \"https://example.com/webhooks/invoice\",\n \"cancel_url\": \"https://example.com/webhooks/invoice\"\n}"
response = http.request(request)
puts response.read_body{
"object": "checkout_session",
"id": "obj_2P9K3sample",
"url": "https://example.com/webhooks/invoice"
}{
"type": "https://errors.invoiceapi.mx/auth_unauthorized",
"title": "Authentication required",
"status": 401,
"code": "auth.unauthorized",
"detail": "Missing or invalid API key.",
"remediation": "Send `Authorization: Bearer sk_test_...` (or sk_live_...) with a valid API key.",
"doc_url": "/docs/errors#auth-unauthorized",
"request_id": "req_2P9K3sample"
}{
"type": "https://errors.invoiceapi.mx/idempotency_key_reuse",
"title": "Idempotency-Key reused with a different request body",
"status": 409,
"code": "idempotency.key_reuse",
"detail": "This Idempotency-Key was already used for a different payload.",
"remediation": "Reuse an Idempotency-Key only for byte-identical retries; use a fresh key otherwise.",
"doc_url": "/docs/errors#idempotency-key_reuse",
"request_id": "req_2P9K3sample"
}{
"type": "https://errors.invoiceapi.mx/request_validation_failed",
"title": "Request validation failed",
"status": 422,
"code": "request.validation_failed",
"detail": "One or more fields did not satisfy the schema.",
"remediation": "Fix the fields listed in `errors` and resubmit.",
"doc_url": "/docs/errors#request-validation_failed",
"request_id": "req_2P9K3sample"
}{
"type": "https://errors.invoiceapi.mx/rate_limit_exceeded",
"title": "Rate limit exceeded",
"status": 429,
"code": "rate_limit.exceeded",
"detail": "Too many requests for this key + request class (reads and writes are limited separately).",
"remediation": "Back off and retry after the number of seconds in the Retry-After header; batch work or lower your request rate.",
"doc_url": "/docs/errors#rate_limit-exceeded",
"request_id": "req_2P9K3sample"
}{
"type": "https://errors.invoiceapi.mx/internal_error",
"title": "Internal server error",
"status": 500,
"code": "internal.error",
"detail": "An unexpected error occurred.",
"remediation": "Retry later; contact support with the request_id if it persists.",
"doc_url": "/docs/errors#internal-error",
"request_id": "req_2P9K3sample"
}billing
Start a subscription checkout
Creates a hosted checkout session for a paid plan (starter, growth, scale) and returns its URL — send the browser there to pay. On completion the webhook activates the plan. An organization with an active subscription changes plans through the billing portal instead.
POST
/
v1
/
billing
/
checkout_sessions
Start a subscription checkout
curl --request POST \
--url https://api.newinvoice.dev/v1/billing/checkout_sessions \
--header 'Authorization: Bearer <token>' \
--header 'Content-Type: application/json' \
--data '
{
"plan": "starter",
"success_url": "https://example.com/webhooks/invoice",
"cancel_url": "https://example.com/webhooks/invoice"
}
'import requests
url = "https://api.newinvoice.dev/v1/billing/checkout_sessions"
payload = {
"plan": "starter",
"success_url": "https://example.com/webhooks/invoice",
"cancel_url": "https://example.com/webhooks/invoice"
}
headers = {
"Authorization": "Bearer <token>",
"Content-Type": "application/json"
}
response = requests.post(url, json=payload, headers=headers)
print(response.text)const options = {
method: 'POST',
headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
body: JSON.stringify({
plan: 'starter',
success_url: 'https://example.com/webhooks/invoice',
cancel_url: 'https://example.com/webhooks/invoice'
})
};
fetch('https://api.newinvoice.dev/v1/billing/checkout_sessions', options)
.then(res => res.json())
.then(res => console.log(res))
.catch(err => console.error(err));<?php
$curl = curl_init();
curl_setopt_array($curl, [
CURLOPT_URL => "https://api.newinvoice.dev/v1/billing/checkout_sessions",
CURLOPT_RETURNTRANSFER => true,
CURLOPT_ENCODING => "",
CURLOPT_MAXREDIRS => 10,
CURLOPT_TIMEOUT => 30,
CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
CURLOPT_CUSTOMREQUEST => "POST",
CURLOPT_POSTFIELDS => json_encode([
'plan' => 'starter',
'success_url' => 'https://example.com/webhooks/invoice',
'cancel_url' => 'https://example.com/webhooks/invoice'
]),
CURLOPT_HTTPHEADER => [
"Authorization: Bearer <token>",
"Content-Type: application/json"
],
]);
$response = curl_exec($curl);
$err = curl_error($curl);
curl_close($curl);
if ($err) {
echo "cURL Error #:" . $err;
} else {
echo $response;
}package main
import (
"fmt"
"strings"
"net/http"
"io"
)
func main() {
url := "https://api.newinvoice.dev/v1/billing/checkout_sessions"
payload := strings.NewReader("{\n \"plan\": \"starter\",\n \"success_url\": \"https://example.com/webhooks/invoice\",\n \"cancel_url\": \"https://example.com/webhooks/invoice\"\n}")
req, _ := http.NewRequest("POST", url, payload)
req.Header.Add("Authorization", "Bearer <token>")
req.Header.Add("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)
defer res.Body.Close()
body, _ := io.ReadAll(res.Body)
fmt.Println(string(body))
}HttpResponse<String> response = Unirest.post("https://api.newinvoice.dev/v1/billing/checkout_sessions")
.header("Authorization", "Bearer <token>")
.header("Content-Type", "application/json")
.body("{\n \"plan\": \"starter\",\n \"success_url\": \"https://example.com/webhooks/invoice\",\n \"cancel_url\": \"https://example.com/webhooks/invoice\"\n}")
.asString();require 'uri'
require 'net/http'
url = URI("https://api.newinvoice.dev/v1/billing/checkout_sessions")
http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true
request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n \"plan\": \"starter\",\n \"success_url\": \"https://example.com/webhooks/invoice\",\n \"cancel_url\": \"https://example.com/webhooks/invoice\"\n}"
response = http.request(request)
puts response.read_body{
"object": "checkout_session",
"id": "obj_2P9K3sample",
"url": "https://example.com/webhooks/invoice"
}{
"type": "https://errors.invoiceapi.mx/auth_unauthorized",
"title": "Authentication required",
"status": 401,
"code": "auth.unauthorized",
"detail": "Missing or invalid API key.",
"remediation": "Send `Authorization: Bearer sk_test_...` (or sk_live_...) with a valid API key.",
"doc_url": "/docs/errors#auth-unauthorized",
"request_id": "req_2P9K3sample"
}{
"type": "https://errors.invoiceapi.mx/idempotency_key_reuse",
"title": "Idempotency-Key reused with a different request body",
"status": 409,
"code": "idempotency.key_reuse",
"detail": "This Idempotency-Key was already used for a different payload.",
"remediation": "Reuse an Idempotency-Key only for byte-identical retries; use a fresh key otherwise.",
"doc_url": "/docs/errors#idempotency-key_reuse",
"request_id": "req_2P9K3sample"
}{
"type": "https://errors.invoiceapi.mx/request_validation_failed",
"title": "Request validation failed",
"status": 422,
"code": "request.validation_failed",
"detail": "One or more fields did not satisfy the schema.",
"remediation": "Fix the fields listed in `errors` and resubmit.",
"doc_url": "/docs/errors#request-validation_failed",
"request_id": "req_2P9K3sample"
}{
"type": "https://errors.invoiceapi.mx/rate_limit_exceeded",
"title": "Rate limit exceeded",
"status": 429,
"code": "rate_limit.exceeded",
"detail": "Too many requests for this key + request class (reads and writes are limited separately).",
"remediation": "Back off and retry after the number of seconds in the Retry-After header; batch work or lower your request rate.",
"doc_url": "/docs/errors#rate_limit-exceeded",
"request_id": "req_2P9K3sample"
}{
"type": "https://errors.invoiceapi.mx/internal_error",
"title": "Internal server error",
"status": 500,
"code": "internal.error",
"detail": "An unexpected error occurred.",
"remediation": "Retry later; contact support with the request_id if it persists.",
"doc_url": "/docs/errors#internal-error",
"request_id": "req_2P9K3sample"
}Authorizations
API key: Authorization: Bearer sk_test_... or sk_live_....
Headers
Pin a dated API release (Stripe-style). Omit to use the current version. An unknown value returns 400 request.invalid_version. Echoed back on every response.
Example:
"2026-07-10"
Connect: act on behalf of one of your connected accounts (its acct_…/org_… id). Omit to act as your own organization. Not honored on /v1/api_keys.
Example:
"org_2P9connectedacct"
Safely retry any POST. The first response is stored for 24h and replayed byte-for-byte for identical retries (the replay adds an idempotent-replayed: true header). Reusing the key with a different body is 409 idempotency.key_reuse; an in-flight duplicate is 409 idempotency.key_processing. This makes retrying a 502/429 safe — no duplicate stamp.
Example:
"a1b2c3d4-e5f6-4789-8abc-1234567890ab"
Body
application/json
A purchasable plan (free is the absence of a subscription).
Available options:
starter, growth, scale Where the browser lands after payment; defaults to the dashboard billing page.
Where the browser lands on abandon; defaults to the dashboard billing page.