Changing the way we manage underpaid postage

Learn how the changes to parcel size verification could affect you.

Learn how to accurately calculate your postage

From 31 March 2022, we’ll notify you if any items have been sent with underpaid postage and charge you any difference.

What's changing?

From 31 March 2022, our process to identify and charge for items sent with underpaid postage with MyPost Business will change.

Our parcel processing machines will automatically detect if there are any differences between the postage you have paid for posting your item, and what the correct postage should be.  This is to ensure timely delivery to your customers, and that all customers are paying the correct rate for the delivery of items.

To help you calculate your postage correctly and avoid any notifications of underpaid postage, please see tips below which cover the more frequent reasons we’ve found customers may send an item with underpaid postage, and how to avoid them.

If we identify any items sent with underpaid postage, we’ll notify you of the discrepancies, and send you details on how to view and pay the postage.

Tips to avoid underpaid postage

Ensure you correctly measure your item

The dimensions of your item are important to help us work out your postage based on how much space will be required to transport your item. It’s important that you closely measure the actual item’s outer measurements with a ruler or measuring tape.

Ensure your contents fit properly

If the contents inside your packaging are straining the length, width or height of the packaging, this may impact the cubic volume of your item. As we measure at the largest point, any part protruding will be measured. We also recommend you tape and secure loose ends, ribbons, and flaps to avoid our machines detecting a larger size.

Check the packaging dimensions

When entering the dimensions of your item into MyPost Business, keep in mind that the dimensions printed on the outside of the packaging are often the internal dimensions. To find the accurate external dimensions of items, we recommend you use a ruler or tape measure to measure your parcels.

Ensure your item weighs 5kgs or less

When sending with our “If it Packs, It Posts” packaging to be eligible for the flat rate postage. Our scanners will detect any items over 5kgs and calculate the difference in postage. You’ll also need to make sure you accurately select the size of the packaging (small, medium, large or extra large) you are using when purchasing your postage in MyPost Business.

How it works


Our parcel processing machines will automatically detect if the parcel’s weight and dimensions are different to what was declared and paid for on the label.


If any items have underpaid postage, we'll add the difference to your MyPost Business account.

Review & pay

The item will be delivered and you'll have 28 days to pay the outstanding amount.

Watch this video to view underpaid postage identified in MyPost Business

Toolkits and how-tos

Measuring your parcels

Learn how to accurately measure your parcel’s weight and dimensions and calculate the correct postage.

How postage is calculated

We use both a parcel's weight and its dimensions to determine how much space it will take up in our vehicles. When you enter the correct weight and parcel dimensions, it helps us ensure your parcel moves through our network as efficiently as possible, and that you’re charged correctly.

If you’re using our If It Packs, It Posts satchels or boxes, we’ll check that the measurements correspond to the size of that particular packaging, and the item weighs under 5kgs.