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.