Technical Requirements & Mandatory Data

🎯 Purpose

This document outlines the mandatory data, technical requirements, and integration expectations for organizations connecting to Link4 to send and receive electronic invoices and related documents.

Before starting integration, clients must ensure that all mandatory information described below is available and accurate in their ERP, Accounting System, or Middleware.

Missing or incorrect data may result in:

• Invoice rejection

• Validation errors

• Delivery failures with authorities such as UAE FTA or Peppol networks

1️⃣ Supported Integration Method

API Integration

Your system (ERP, Accounting Software, or Middleware) connects securely to Link4 via API.

Requirements

• API endpoints provided by Link4

• Authentication method (OAuth or API keys)

• Payload structure compliance

• Validation rule adherence

2️⃣ Transaction Types Supported

Link4 supports the following document types:

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., FTA)

• Delivery and notifications

3.1  Mandatory Fields – Supplier

• Legal name

• Trade name

• Address

• Emirate

• Country

• Phone

• Email

• TRN (Tax Registration Number – Mandatory)

3.2 Mandatory Fields – Buyer

• Legal name

• Address

• Country

• TRN (If VAT registered)

3.3 Providing 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

• Unique reference column may be required for create/update logic

• Column order and format will be provided by Link4

4️⃣Document Header Requirements

5️⃣Line Level Field Requirements

Below is the structured list of line-level data requirements.

5.1 Mandatory Fields

Core Identification

• Line number

• Item/service description

Quantity & Pricing

• Quantity

• Unit of measure

• Unit price

• Line net amount

• Discount amount (0 if none)

Tax

• VAT rate (5% / 0% / Exempt)

• VAT category

• VAT amount

• Line total (Inclusive of VAT)

Exemption (Only if 0% / Exempt)

• Exemption reason code

• Exemption reason text

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5.2 Optional Fields

Product Information

• Item code / SKU

• HS / Customs code

• Product classification

• Country of origin

Pricing / Finance

• Cost price

• Markup

• Selling price

• Currency exchange rate

• Foreign currency value

Compliance / Metadata

• Accounting code

• Ledger code

• Reporting category

• Line notes

• Digital signature hash

• Attachment references

6️⃣ API Integration Requirements

6.1 Authentication

• Secure credentials (OAuth or API keys)

• Required permissions for read and write operations

6.2 Data Coverage

Your system must provide:

• Header data

• Line items

• Tax information

• Contact data resolvable via unique IDs

6.3 System Behaviour

• Duplicate documents must be avoided

• Clear error responses (HTTP status + message)

• Stable document identifiers for retries and reprocessing

7️⃣ Validation & Submission

All documents are validated against:

• FTA VAT Law

• Customs regulations

• Free zone rules

• Emirate-specific reporting requirements

• Clearance-ready design standards

Missing or invalid data may result in:

• Document rejection

• Validation errors

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

⚠️ Common Rejection Causes

• Missing TRN

• Missing Emirate

• Incorrect VAT calculation

• Missing exemption code