What this means
If you see an error like:
“Package weight 10kg exceeds maximum weight 5kg for Flat Rate Packages (FLAT_RATE_BOX_MEDIUM)”
It means the total weight of your order is over 5kg, which is the maximum allowed for Australia Post Flat Rate packaging.
How to fix it
You have two options:
1. Use your own packaging
Change the package type from Flat Rate to your own packaging option.
2. Adjust the order weight
Reduce the total order weight to 5kg or less — but only if the actual parcel weight is within this limit.
Important
Do not manually lower the weight just to access Flat Rate pricing.
If the parcel actually weighs more than 5kg:
Australia Post may apply an Underpaid Postage charge
Additional fees can be incurred
Always ensure the weight entered matches the actual parcel weight to avoid extra costs.