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Arrears billing flips the default: instead of charging at the start of a billing period, we charge at the end. The customer uses the service first and pays for what they used.

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When to use arrears

  • Usage-based billing — you meter API calls, seats, or transactions during the month, then bill based on actual usage
  • Enterprise contracts — the customer has net-30 or net-60 payment terms
  • Trials converting to paid — bill after the first period so the customer experiences the value before the first charge
  • Credit-gated models — customer has a credit limit; you bill after confirming usage

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How it works

With billing_mode: "advance" (default), the invoice is created at the start of the period: 
June 1: Invoice created → charge → period begins
June 30: Period ends
July 1: Next invoice created → charge → new period begins
With billing_mode: "arrears": 
June 1: Period begins (no invoice yet)
June 30: Period ends
July 1: Invoice created → charge → new period begins
The invoice and payment logic are identical — it’s only the timing that differs.
Advance (default)Arrears
Invoice createdStart of periodEnd of period
Customer paysBefore using serviceAfter using service
Grace / dunningSameSame (starts after invoice is created)
next_bill_at meaningNext charge dateNext invoice creation date

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Setting up arrears billing

Add billing_mode: "arrears" when creating the subscription: 
curl -X POST https://api.useplinth.com/v1/subscriptions \
  -H "Authorization: Bearer sk_test_DOCS_SHARED_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "customer_id": "cus_01JXYZ...",
    "plan_id": "plan_enterprise_01...",
    "payment_method": "transfer",
    "billing_mode": "arrears"
  }'
Response
{
  "id": "sub_01JABC...",
  "state": "active",
  "billing_mode": "arrears",
  "current_period_start": "2026-06-01T00:00:00Z",
  "current_period_end": "2026-07-01T00:00:00Z",
  "next_bill_at": "2026-07-01T00:00:00Z"
}
next_bill_at is July 1st — that’s when the June invoice is created and the July period begins simultaneously.
The Postpaid preset applies arrears billing along with a longer grace period (14 days) and more lenient dunning settings. If you’re doing enterprise billing, applying the Postpaid preset first is quicker than configuring each knob. See Presets.