eBay Postage Helper

A Go utility for managing eBay listing postage/shipping costs, specifically designed for Australian sellers shipping to the United States with the current IEEPA tariff regime.

Features

• Shipping Calculator: Calculate total US shipping costs including:

  • Australia Post international rates (Zone 3 - USA/Canada)
  • US IEEPA tariffs based on country of origin
  • Zonos processing fees
  • Extra Cover (insurance) options

• Brand → Country Mapping: Automatic lookup of country of origin by brand name

• eBay Integration:

  • OAuth2 authentication with eBay API
  • View active listings with current postage settings
  • Compare current vs calculated postage amounts
  • Bulk update shipping cost overrides (Phase 2)

Quick Start

1. Build

go build -o ebay-postage-helper ./cmd/server

2. Configure eBay Credentials

Set environment variables for your eBay Developer API credentials:

export EBAY_CLIENT_ID="your-client-id"
export EBAY_CLIENT_SECRET="your-client-secret"
export EBAY_REDIRECT_URI="http://localhost:8080/api/oauth/callback"

3. Run

# Sandbox mode (default)
./ebay-postage-helper

# Production mode
./ebay-postage-helper -sandbox=false

# Custom port
./ebay-postage-helper -port=3000

4. Open Browser

Navigate to http://localhost:8080

API Endpoints

Endpoint	Method	Description
/api/health	GET	Health check
/api/auth/url	GET	Get eBay OAuth URL
/api/auth/status	GET	Check auth status
/api/oauth/callback	GET	OAuth callback handler
/api/calculate	POST	Calculate shipping costs
/api/brands	GET	List available brands
/api/weight-bands	GET	List weight bands
/api/tariff-countries	GET	List tariff rates by country
/api/inventory	GET	Get eBay inventory items
/api/offers	GET	Get eBay offers/listings
/api/policies	GET	Get fulfillment policies
/api/update-shipping	POST	Update shipping overrides

Calculation Logic

Total US Shipping Formula

Total = AusPost Shipping + Extra Cover (optional) + Tariff Duties + Zonos Fees

Where:

• AusPost Shipping = Base Rate × (1 + 2% handling) × (1 - discount band)
• Extra Cover = ((ItemValue - $100) / 100) × $4 × (1 - discount)
• Tariff Duties = Item Value × Tariff Rate
• Zonos Fees = (Tariff Duties × 10%) + $1.69

Current Tariff Rates (US IEEPA)

Country	Rate
India	50%
Mexico	25%
China	20%
Vietnam	20%
Indonesia	19%
Malaysia	19%
Japan	15%
Australia	10%
United States	0%

Weight Bands (Zone 3 - USA/Canada)

Band	Weight	Base Price (AUD)
XSmall	< 250g	$22.30
Small	250 - 500g	$29.00
Medium	500g - 1kg	$42.20
Large	1 - 1.5kg	$55.55
XLarge	1.5 - 2kg	$68.85

Project Structure

ebay-helpers/
├── cmd/server/
│   ├── main.go              # Entry point
│   └── web/                  # Embedded frontend
│       ├── index.html
│       └── app.js
├── internal/
│   ├── calculator/          # Shipping cost calculations
│   │   ├── calculator.go
│   │   └── data.go
│   ├── ebay/                # eBay API client
│   │   └── client.go
│   └── handlers/            # HTTP handlers
│       └── handlers.go
├── src/data/                # Reference JSON data
├── go.mod
├── go.sum
└── TariffAndPostalCalculator.xlsx  # Original spreadsheet

Roadmap

Phase 1 (Current)

• Shipping cost calculator
• eBay OAuth integration
• View listings with postage comparison
• Reference data display

Phase 2 (Next)

• Bulk edit shipping overrides
• Item weight/brand detection from titles
• Fulfillment policy management
• Export/import configuration

Future

• Live AusPost rate fetching
• Zonos API integration
• Multiple marketplace support
• Price history tracking

Data Sources

• Postal Rates: Australia Post International Parcel rates
• Tariff Rates: US IEEPA Reciprocal Tariffs (2025)
• Zonos Fees: Zonos customs clearance processing