A 28 day expiry plan does not bill once a calendar month. It gives you a fixed block of credit and 28 days to use it, and when the 28 days are up the unused balance is gone unless you roll it over. Over a year that works out to about 13 recharges rather than 12, so the real yearly cost is higher than the headline monthly number times twelve.
Boost sells its plans this way. Its Critical Information Summary lists the 28 day expiry plans by recharge amount, and the provider describes the cycle in days rather than in billing months. The practical effect is simple: if you let a cycle lapse you lose the remaining credit, so the job is to put the next recharge in before the expiry date.
How many recharges a 28 day cycle means in a year
Thirteen. A 365 day year contains thirteen full 28 day cycles. That is why comparing a prepaid plan against a monthly postpaid plan on the headline price alone understates the prepaid cost: you pay for thirteen cycles, not twelve.
Which Boost recharges are on the 28 day cycle
| Recharge amount | Data allowance | Download speed cap |
|---|---|---|
| $28 | 8GB | 150Mbps |
| $39 | 30GB | 150Mbps |
| $49 | 45GB | 150Mbps |
| $59 | 55GB | 250Mbps |
| $74 | 100GB | Uncapped |
These are the 28 day expiry columns from the Critical Information Summary. The provider states the same figures in its own price list and warns that plan prices may change.
What happens at the end of the cycle
Recharging before expiry is what keeps the service alive and, on most of these recharges, rolls the unused data into the next cycle. The provider states that rollover applies when you recharge the $28, $39, $49, $59 or $74 amounts before expiry. Miss the date and the balance does not carry over automatically.
There is a longer tail here as well: if the prepaid SIM sits fully expired, the provider states it is automatically deactivated six months after the expiry date of the last recharge. If you want to keep the number you need to keep the service recharged or transfer it to another provider.
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.
Use the comparison tool on this site to see how many recharges a plan needs over a year and what that costs, rather than working it out by hand.