Invoice Generator API

We created a simple API at Invoice-Generator.com to generate invoice PDFs on the fly. This service has been used internally by us for some time. We believe this could be helpful in your project as well.

The API has a primary endpoint that returns a PDF given details of an invoice. We don't store any of your invoice data.

In addition to PDF, the API can also generate e-invoices in UBL (Universal Business Language) with the invoice PDF embedded. This is useful as the world shifts to e-invoicing because UBL invoices are tricky to generate.

Use Cases

• Creating invoices for VAT compliance
• Generate a PDF of an invoice that you have the details to (recipient, line items, etc)
• Produce invoices for B2B buyers from an order or receipt
• Selling products or services on credit terms
• Creating e-invoices in UBL (Universal Business Language)

Build with AI

AI assistants can create prefilled Invoice Generator documents directly from a conversation—no API integration required.

Use our public AI instructions to learn how to create prefilled invoices, quotes, estimates, receipts, timesheets, and other supported documents.

View AI Assistant Documentation →

For authenticated, programmatic document generation, continue with the API documentation below.

Getting Started

In order to begin using the Invoice-Generator.com API, you first need to create an API key. The process for obtaining an API key is as follows.

1. Create a free Invoice-Generator.com account here, or sign in if you already have one.
2. Go to the Developer Settings page (Settings > Developer).
3. In the "API Keys" section, click New to generate an API key.

Now you have an API key and are ready to start invoicing!

A machine-readable OpenAPI specification is available as YAML or JSON and can be imported into API clients such as Postman, Insomnia, or Bruno.

The free API plan has a limit of 100 invoices per month. In order to generate more invoices you will need to purchase an API subscription.

Examples

Simple Invoice

curl https://invoice-generator.com \
  -H "Authorization: Bearer myApiKey" \
  -d from="Nikolaus Ltd" \
  -d to="Acme, Corp." \
  -d logo="https://example.com/img/logo-invoice.png" \
  -d number=1 \
  -d date="Feb 9, 2015" \
  -d due_date="Feb 16, 2015" \
  -d "items[0][name]"="Starter plan monthly" \
  -d "items[0][quantity]"=1 \
  -d "items[0][unit_cost]"=99 \
  -d notes="Thanks for being an awesome customer\!" \
  -d terms="Please pay by the due date." \
> invoice.pdf

VAT Invoice

Here's a simple cURL example for generating invoices with VAT:

curl https://invoice-generator.com \
  -H "Authorization: Bearer myApiKey" \
  -d from="Nikolaus Ltd%0AVAT ID: 1234" \
  -d to="Foster Moen%0AVAT ID: 4567" \
  -d logo="https://example.com/img/logo-invoice.png" \
  -d number=1 \
  -d date="Feb 9, 2015" \
  -d payment_terms="Charged - Do Not Pay" \
  -d "items[0][name]"="Starter Plan Monthly" \
  -d "items[0][quantity]"=1 \
  -d "items[0][unit_cost]"=99 \
  -d tax_title="VAT" \
  -d "fields[tax]"="%" \
  -d tax=8 \
  -d notes="Thanks for being an awesome customer\!" \
  -d terms="No need to submit payment. You will be auto-billed for this invoice." \
> invoice.vat.pdf

JSON Input

JSON input is also accepted with the Content-Type header set to application/json

curl https://invoice-generator.com \
  -H "Authorization: Bearer myApiKey" \
  -H "Content-Type: application/json" \
  -d '{"from":"Nikolaus Ltd","to":"Acme, Corp.","logo":"https://example.com/img/logo-invoice.png","number":1,"items":[{"name":"Starter plan","quantity":1,"unit_cost":99}],"notes":"Thanks for your business!"}' \
> invoice.pdf

Localization

It is possible to change the localization used to generate the invoice by supplying a locale in the Accept-Language header. The default locale is en-US.

curl https://invoice-generator.com \
  -H "Authorization: Bearer myApiKey" \
  -H "Accept-Language: fr-FR" \
  -d from="Nikolaus Ltd" \
  -d to="Acme Corp." \
  -d logo="https://example.com/img/logo-invoice.png" \
  -d number=1 \
  -d currency=eur \
  -d date="Feb 9, 2015" \
  -d due_date="Feb 16, 2015" \
  -d "items[0][name]"="Starter plan monthly" \
  -d "items[0][quantity]"=1 \
  -d "items[0][unit_cost]"=99 \
> invoice.pdf

Supported Languages

We currently have translations available in English, French, German, Spanish, and Thai.

Custom Fields

curl https://invoice-generator.com \
  -H "Authorization: Bearer myApiKey" \
  -d from="Nikolaus Ltd" \
  -d to="My Customer" \
  -d ship_to="Shipping Address" \
  -d logo="https://example.com/img/logo-invoice.png" \
  -d number=1 \
  -d date="Feb 9, 2015" \
  -d "custom_fields[0][name]"="My Custom Field" \
  -d "custom_fields[0][value]"="Some Value" \
  -d "items[0][name]"="Starter Plan Monthly" \
  -d "items[0][quantity]"=1 \
  -d "items[0][unit_cost]"=99 \
> invoice.custom_fields.pdf

Theme

Invoice appearance can be classic (default) or slate.

curl https://invoice-generator.com \
  -H "Authorization: Bearer myApiKey" \
  -d from="Nikolaus Ltd" \
  -d to="Acme, Corp." \
  -d theme=slate \
  -d number=1 \
  -d "items[0][name]"="Starter plan monthly" \
  -d "items[0][quantity]"=1 \
  -d "items[0][unit_cost]"=99 \
> invoice.slate.pdf

E-invoice

Here's a simple cURL example for generating e-invoices in UBL XML:

curl https://invoice-generator.com/ubl \
  -H "Authorization: Bearer myApiKey" \
  -d from="Nikolaus Ltd%0AVAT ID: 1234" \
  -d to="Foster Moen%0AVAT ID: 4567" \
  -d logo="https://example.com/img/logo-invoice.png" \
  -d number=1 \
  -d date="Feb 9, 2015" \
  -d date="Mar 9, 2015" \
  -d payment_terms="NET 30" \
  -d "items[0][name]"="Starter Plan Monthly" \
  -d "items[0][quantity]"=1 \
  -d "items[0][unit_cost]"=99 \
  -d tax_title="VAT" \
  -d "fields[tax]"="%" \
  -d tax=8 \
  -d notes="Thanks for being an awesome customer\!" \
> invoice.xml

---

API Reference

All document types use the same endpoint. Send type to choose the document. When type is omitted, the API creates an invoice.

POST https://invoice-generator.com

Shared Parameters

These fields apply to every document type. When a value is null or zero, the field will not be shown. The exception to this are the required fields from, to, date, and items.

Parameter	Description	Default Value
theme	Invoice appearance: classic or slate	classic
logo	URL of your logo	null
from	Your organization billing address and contact info	null
to	Entity being billed - multiple lines ok	null
ship_to	Shipping address - multiple lines ok	null
number	Document number	null
currency	ISO 4217 3-digit currency code	USD
custom_fields	Array of objects - see Custom Field Parameters	[]
date	Document date	current date
items	Array of objects - see Line Item Parameters	[]
fields	Object - see Subtotal Line Parameters	{"tax":"%","discounts":false,"shipping":false}
discounts	Subtotal discounts - numbers only	0
tax	Tax - numbers only	0
shipping	Shipping - numbers only	0
notes	Notes - any extra information not included elsewhere	null
terms	Terms and conditions - all the details	null

Line Item Parameters

Line items are represented as an array of objects. Here's an example:

{
  "items": [
    {
      "name": "Gizmo",
      "quantity": 10,
      "unit_cost": 99.99,
      "description": "The best gizmos there are around."
    },
    {
      "name": "Gizmo v2",
      "quantity": 5,
      "unit_cost": 199.99
    }
  ]
}

Optional line item fields date, reference, and payment may also be sent.

Subtotal Line Parameters

The fields object toggles the discounts, tax, and shipping subtotal lines. Each setting can have a value of %, true, or false. For example to add a percent tax rate and flat shipping to your invoice you would send this:

{
  "fields": {
    "tax": "%",
    "discounts": false,
    "shipping": true
  },
  "tax": 7,
  "shipping": 15
}

Custom Field Parameters

Custom fields allow you to add additional fields to the invoice details in the top-right. Here's an example:

{
  "custom_fields": [
    {
      "name": "Gizmo",
      "value": "PO-1234"
    },
    {
      "name": "Account Number",
      "value": "CUST-456"
    }
  ]
}

Template Parameters

These parameters control the titles of the fields on the template. If localization is used, the default values are translated to the specified language. Any template parameter given will override the localized default. Type-specific titles are listed on each create section below.

Parameter	Default Value
header	INVOICE
to_title	Bill To
ship_to_title	Ship To
number_title	#
date_title	Date
payment_terms_title	Payment Terms
due_date_title	Due Date
purchase_order_title	Purchase Order
quantity_header	Quantity
item_header	Item
unit_cost_header	Rate
amount_header	Amount
subtotal_title	Subtotal
discounts_title	Discounts
tax_title	Tax
shipping_title	Shipping
total_title	Total
amount_paid_title	Amount Paid
balance_title	Balance
terms_title	Terms
notes_title	Notes

Create Invoice

POST https://invoice-generator.com

type defaults to invoice and can be omitted. Uses Shared Parameters plus:

Parameter	Description	Default Value
purchase_order	Purchase order number	null
payment_terms	Payment terms summary (i.e. NET 30)	null
due_date	Invoice due date	null
amount_paid	Amount paid - numbers only	0
payment_methods	Array of payment method objects. UBL uses { "type": "url", "name": "...", "url": "..." }. Not shown on the PDF.	[]

{
  "type": "invoice",
  "from": "Nikolaus Ltd",
  "to": "Acme, Corp.",
  "number": 1,
  "purchase_order": "PO-1234",
  "items": [{"name": "Starter plan", "quantity": 1, "unit_cost": 99}]
}

Create Receipt

POST https://invoice-generator.com

Set type to receipt. Uses Shared Parameters plus:

Parameter	Description	Default Value
purchase_order	Referenced invoice number	null
payment_terms	Payment method summary	null
due_date	Date paid	null
amount_paid	Amount received - numbers only	0
payment_methods	Array of payment method objects. UBL uses { "type": "url", "name": "...", "url": "..." }. Not shown on the PDF.	[]

Parameter	Default Value
header	RECEIPT
number_title	Receipt #
to_title	Received From
due_date_title	Date Paid
amount_paid_title	Amount Received
payment_terms_title	Payment Method
purchase_order_title	Referenced Invoice

{
  "type": "receipt",
  "from": "Nikolaus Ltd",
  "to": "Acme, Corp.",
  "number": 1,
  "amount_paid": 99,
  "items": [{"name": "Starter plan", "quantity": 1, "unit_cost": 99}]
}

Create Credit Note

POST https://invoice-generator.com

Set type to credit_note. Uses Shared Parameters plus:

Parameter	Description	Default Value
purchase_order	Referenced invoice number	null
amount_refunded	Amount refunded - numbers only	0

This type does not accept due_date, payment_terms, amount_paid, or payment_methods.

Parameter	Default Value
header	CREDIT NOTE
number_title	#
amount_paid_title	Refunded
purchase_order_title	Referenced Invoice

{
  "type": "credit_note",
  "from": "Nikolaus Ltd",
  "to": "Acme, Corp.",
  "number": "CN-1",
  "purchase_order": "1",
  "amount_refunded": 25,
  "items": [{"name": "Unused time", "quantity": 1, "unit_cost": 25}]
}

Create Quote

POST https://invoice-generator.com

Set type to quote. Uses Shared Parameters plus:

Parameter	Description	Default Value
purchase_order	Purchase order number	null
payment_terms	Payment terms summary	null

Parameter	Default Value
header	QUOTE
number_title	Quote #

{
  "type": "quote",
  "from": "Nikolaus Ltd",
  "to": "Acme, Corp.",
  "number": 1,
  "payment_terms": "Valid for 30 days",
  "items": [{"name": "Website redesign", "quantity": 1, "unit_cost": 2500}]
}

Create Estimate

POST https://invoice-generator.com

Set type to estimate. Uses Shared Parameters plus:

Parameter	Description	Default Value
purchase_order	Purchase order number	null
payment_terms	Valid-until summary	null

Parameter	Default Value
header	ESTIMATE
number_title	Estimate #
payment_terms_title	Valid Until

{
  "type": "estimate",
  "from": "Nikolaus Ltd",
  "to": "Acme, Corp.",
  "number": 1,
  "payment_terms": "30 days",
  "items": [{"name": "Repair work", "quantity": 4, "unit_cost": 75}]
}

Create Pro Forma Invoice

POST https://invoice-generator.com

Set type to proforma_invoice. Uses Shared Parameters plus:

Parameter	Description	Default Value
purchase_order	Purchase order number	null
payment_terms	Payment terms summary	null

Parameter	Default Value
header	PROFORMA INVOICE
number_title	Proforma #

{
  "type": "proforma_invoice",
  "from": "Nikolaus Ltd",
  "to": "Acme, Corp.",
  "number": 1,
  "items": [{"name": "Deposit", "quantity": 1, "unit_cost": 500}]
}

Create Purchase Order

POST https://invoice-generator.com

Set type to purchase_order. Uses Shared Parameters plus:

Parameter	Description	Default Value
payment_terms	Payment terms summary	null
due_date	Required-by date	null

This type does not accept a purchase_order value field.

Parameter	Default Value
header	PURCHASE ORDER
number_title	Purchase Order #
due_date_title	Required By

{
  "type": "purchase_order",
  "from": "Acme, Corp.",
  "to": "Nikolaus Ltd",
  "number": 1,
  "due_date": "Mar 1, 2015",
  "items": [{"name": "Office chairs", "quantity": 4, "unit_cost": 120}]
}

Create Statement

POST https://invoice-generator.com

Set type to statement. Uses Shared Parameters plus:

Parameter	Description	Default Value
purchase_order	Purchase order number	null
payment_terms	Period start	null
due_date	Period end	null
amount_paid	Opening balance - numbers only	0
payment_methods	Array of payment method objects. Not shown on the PDF.	[]

Line items should include date, reference, and payment where relevant.

Parameter	Default Value
header	STATEMENT
number_title	Statement #
to_title	Statement To
payment_terms_title	Period Start
due_date_title	Period End
amount_paid_title	Opening Balance
subtotal_title	Total Charges
item_header	Description
amount_header	Balance
date_header	Date
reference_header	Reference
charges_header	Charges
payments_header	Payments
payments_title	Total Payments

{
  "type": "statement",
  "from": "Nikolaus Ltd",
  "to": "Acme, Corp.",
  "number": 1,
  "payment_terms": "Jan 1, 2015",
  "due_date": "Jan 31, 2015",
  "items": [
    {"name": "Invoice 12", "date": "Jan 8, 2015", "reference": "12", "unit_cost": 99, "quantity": 1, "payment": 0}
  ]
}

Create Timesheet

POST https://invoice-generator.com

Set type to timesheet. Uses Shared Parameters plus:

Parameter	Description	Default Value
purchase_order	Purchase order number	null
payment_terms	Period start	null
due_date	Period end	null
amount_paid	Amount paid - numbers only	0
payment_methods	Array of payment method objects. Not shown on the PDF.	[]

Line items typically use date and treat quantity as hours.

Parameter	Default Value
header	TIMESHEET
number_title	Timesheet #
to_title	Timesheet To
payment_terms_title	Period Start
due_date_title	Period End
quantity_header	Hours
item_header	Description
subtotal_title	Total Hours
date_header	Date

{
  "type": "timesheet",
  "from": "Nikolaus Ltd",
  "to": "Acme, Corp.",
  "number": 1,
  "items": [
    {"name": "Development", "date": "Jan 8, 2015", "quantity": 6, "unit_cost": 85}
  ]
}

Create Work Order

POST https://invoice-generator.com

Set type to work_order. Uses Shared Parameters plus:

Parameter	Description	Default Value
ship_to	Job site address - multiple lines ok	null
payment_terms	Technician	null
due_date	Scheduled date	null

This type does not accept a purchase_order value field.

Parameter	Default Value
header	WORK ORDER
number_title	Work Order #
ship_to_title	Job Site
payment_terms_title	Technician
due_date_title	Scheduled Date
terms_title	Authorization

{
  "type": "work_order",
  "from": "Nikolaus Ltd",
  "to": "Acme, Corp.",
  "ship_to": "123 Job Site Rd\nAustin, TX",
  "number": 1,
  "payment_terms": "Alex Rivera",
  "due_date": "Mar 1, 2015",
  "items": [{"name": "HVAC repair", "quantity": 2, "unit_cost": 95}],
  "notes": "This work order authorizes the listed work. It is not an invoice."
}

Create Packing Slip

POST https://invoice-generator.com

Set type to packing_slip. Uses Shared Parameters plus:

Parameter	Description	Default Value
purchase_order	Related invoice number	null

This type does not accept due_date, payment_terms, amount_paid, payment_methods, tax, discounts, or shipping. Line items use name, description, and quantity only (unit_cost is ignored).

Parameter	Default Value
header	PACKING SLIP
number_title	Packing Slip #
purchase_order_title	Invoice #

{
  "type": "packing_slip",
  "from": "Nikolaus Ltd",
  "to": "Acme, Corp.",
  "ship_to": "Warehouse 4\nAustin, TX",
  "number": 1,
  "purchase_order": "INV-88",
  "items": [{"name": "Office chairs", "quantity": 4}]
}

Create E-invoice

POST https://invoice-generator.com/ubl

Uses the same parameters as the matching PDF create section. UBL is supported for invoice, receipt (Invoice XML), and credit_note only. Other types return an error.