Technical Requirements & Mandatory Data

🎯 Purpose

This guide explains the mandatory technical and data requirements for organizations integrating with Link4 to send and receive electronic invoices.

Before integration, ensure your ERP, Accounting System, or Middleware can supply all required data.

Missing or incorrect data will result in:

1. invoice rejection
   
2. validation errors
   
3. delivery failures with authorities such as Peppol Australia (ATO framework) or Peppol networks.
   

1️⃣ Supported Integration Method

API Integration

Your system connects to Link4 via a secure API.

Requirements

• API endpoints provided by Link
  

• Authentication method (OAuth or API keys)
  

• Payload structure compliance
  

• Validation rule adherence

2️⃣ Transaction Types Supported

For all document types, the following data must be complete:

• Document header data

• Supplier and buyer details

• Line items

• Tax information
  

3️⃣ Contact Data Requirements (Buyers & Suppliers)

Accurate contact data is mandatory.

This data is used for:

• Addressing and routing (Peppol)

• Tax authority validation (e.g. ATO Framework)

• Delivery and notifications

3.1 Mandatory Fields (Per Contact)

Applies to BOTH customers and suppliers.      

3.3 How to Provide Contact Data

Option A – API

• Each contact must be retrievable using a unique identifier

• All mandatory fields must be returned

• Used to avoid duplicates and ensure correct matching

Option B – CSV Upload

• CSV must include all mandatory fields

• A unique reference column may be required for create/update logic

• Column order and format will be confirmed by Link4

4️⃣ Tax Information

Tax data must comply with the target jurisdiction (e.g. ATO Framework, Peppol VAT rules).

4.1 Mandatory (Header Level)

• Supplier ABN

• Buyer ABN

• Currency = AUD

• Tax basis (inclusive/exclusive)

5️⃣ Line Level Field Requirements

Required

• Line number

• Description of goods/services

• Quantity (numeric)

• Unit of Measure (EA, HRS, KG, etc.)

• Unit price

• Line extension amount (qty × unit price)

• GST rate (10% or 0%)

• Tax amount

• Line total (incl/excl tax consistent with header)

Optional (Recommended)

• Item code/SKU

• Discount rate/amount

• Order reference

• Buyer item ID

6️⃣ Document Header Requirements

Mandatory

• Unique document number

• Issue date (YYYY-MM-DD)

• Document type (Invoice / Credit Note)

• Supplier details (ABN, legal name, full address)

• Buyer details (ABN or Peppol ID, legal name, full address)

• Currency (AUD unless otherwise agreed)

• Tax-exclusive amount

• Total GST amount

• Tax-inclusive amount

Optional

• Due date

• Order reference (PO number)

• Buyer reference

• Contract or project reference

• Payment terms

• Bank / payment details

• Delivery date

• Internal notes (must comply with Peppol format rules)

7️⃣ API Integration Requirements

Authentication

• Secure credentials (OAuth or API keys)

• Read and write permissions

Data Coverage

• Header data

• Line items

• Tax information

• Contact data via unique ID

System Behaviour

• No duplicate documents 

• Clear HTTP errors

• Stable identifiers for retries

8️⃣ Validation & Submission

All documents are validated against:

• Peppol BIS Billing 3.0

• GST math validation

Missing or invalid data may result in:

• Document rejection

• Validation errors

• Delivery failure (e.g. buyer not on network)