Australian prepaid plans are built for Australia. The terms say so plainly, and roaming is handled as an excluded usage rather than as an included feature, which means the charge comes from a different tariff entirely.
What the terms exclude
- TPG Mobile SIM only plans exclude international roaming outright.
- Boost prepaid plans exclude all use overseas from the unlimited calls and text allowance.
- The Optus prepaid data plan does not include international roaming data at all.
- The Boost plan is only for use in Australia.
Those four statements come from four different provider documents and they point the same way: roaming is outside the plan, and in two cases it is not merely charged extra but excluded from the product.
Why the charge is unpredictable
When roaming is not covered by the plan, the cost comes from the network you visit, not from the plan you hold. Our fact base contains no published roaming tariff for any of these providers, so we do not quote one and we do not estimate one. Anyone giving you a per-MB roaming rate for a prepaid SIM is quoting a rate we cannot verify.
What this means for a trip
If you are leaving Australia for more than a few days, a local eSIM or a roaming add-on is usually the honest answer, and the comparison on this site covers eSIM travel data separately from long-term mobile plans for exactly that reason. A prepaid plan that works well at home is not a travel plan.
What we could not verify. Where a provider has not published a figure we mark it unknown rather than estimate it. Re-read the provider page linked below on the day you decide.