JSON in. Invoice PDF out. Cents as sent.

You searched JSON to invoice PDF. Same mill, second template. The packing-slip route and the invoice route are one URL: POST /v1/render. You change the template name. You send invoice fields. You get application/pdf, US Letter.

This page is the query. The product page for the invoice API is Invoice PDF API. Do not treat them as copies. Here the job is: you have invoice JSON, you want a PDF, and you do not want an HTML invoice renderer.

Amounts are integer cents. 1800 is $18.00. We print the number you posted. We do not parse $18.00 on this template. We do not guess a decimal. Line items carry sku, name, qty, and unit_amount_cents. Optional description. Optional notes.

Tax is printed as sent. tax_cents is a field, not a calculation. Slipmill is not a tax engine. We do not pick a jurisdiction. We do not file. We do not emit a customs commercial invoice. If you need those, compute them upstream or use a product built for the border.

bill_to and from are addresses you already store. invoice_id and date are yours. due_date is optional. currency is a label we print. We do not convert it. The mill is a printer, not a ledger.

Check the payload on the invoice JSON validator before you wire production. That tool does not call /v1/render. A Slipmill key still owns the PDF. Header x-sm-key. Fail closed on a bad key, a bad body, or a spent Starter or Pro cap.

Two locked templates we own. packing-slip for the box. invoice for the bill. Branding is a name, an optional hex, and on paid plans a logo URL. You do not upload HTML. You do not design a plate. Get a key and POST.

If you also need the sheet that rides in the carton, keep the same key and switch template to packing-slip. Do not send both jobs in one body. One POST is one PDF. The mill does not merge a slip and a bill onto a single page.

curl

POST /v1/render with x-sm-key. template invoice.

curl -X POST https://slipmill.com/v1/render \
  -H "x-sm-key: YOUR_SLIPMILL_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "template": "invoice",
    "brand": {
      "name": "Northline Goods",
      "accent": "#9E2A22"
    },
    "data": {
      "invoice_id": "INV-2208",
      "date": "2026-08-31",
      "bill_to": {
        "name": "Cedar & Pine Outfitters",
        "address": "440 Warehouse Ave, Dock 3",
        "city": "Newark",
        "region": "NJ",
        "postal": "07105",
        "country": "US"
      },
      "from": {
        "name": "Northline Goods",
        "address": "18 Mercer Street, Hoboken, NJ 07030"
      },
      "items": [
        {
          "sku": "TOTE-12",
          "name": "Canvas tote — natural",
          "qty": 12,
          "unit_amount_cents": 1800
        }
      ],
      "currency": "USD",
      "tax_cents": 0
    }
  }' \
  --output invoice.pdf