What does the foreign-SIM 120-day clock do?
Fleets often fit devices with SIMs that come from another country. The CST IoT Regulations (third version, July 2024), checked in the official text on 3 Nov 2026, allow a foreign SIM in an IoT device for up to 120 days (Art. 5-5). The SIM has to be replaced with a local one (Art. 5-5-1). While a device is on a foreign SIM it is limited to pre-defined applications without unrestricted internet (Art. 5-5-2).
This tool keeps the count for you. You give it the activation date of each SIM. It works out the deadline, sorts the SIMs by days left, lists the ones that are over or cross the limit inside your warning window, and plans the swap visits.
The period, the replacement rule and the scope were checked in the official CST text on 3 Nov 2026. The counting method is not stated there: confirm it with your SIM provider. The page does not say that any device, SIM or provider meets the rule. To check a provider, ask whether it is on the regulator's list.
What do you need to fill in?
| Input | Where to find it | Tip |
|---|---|---|
| Activation date | SIM provider portal, activation e-mail, first report in your platform | Use the date the SIM went live, not the purchase or delivery date. |
| SIM origin | SIM contract, operator name on the SIM | Leave it as unknown until you have checked. Unknown SIMs have no clock. |
| Period and warning window | The official text, your own planning rule | A wider window gives installers more time. 30 days is a starting point. |
| Swaps per working day | Your installers' schedule | Count vehicles reached and finished, not only visits. |
| Days until local SIMs arrive | Your SIM provider | Include activation and delivery to the workshop. |
How is the clock calculated?
- Over the limit: days left below zero.
- Crosses soon: zero up to the warning window. Zero means today is the last allowed day.
- Inside the limit: more days left than the warning window.
A SIM whose deadline falls before the first swap day cannot be saved by more capacity. The plan counts it as late and says so.
Worked example
- A SIM was activated on 1 Jul 2026 and you check on 27 Oct 2026. July has 31 days, so 1 Jul + 30 = 31 Jul, + 31 = 31 Aug (61), + 30 = 30 Sep (91), + 29 = 29 Oct (120). The deadline is 29 Oct 2026, 2 days left, day 118 of 120. With a 30-day window it is listed as crossing soon.
- You have 25 foreign SIMs to move, 5 swaps a day, Friday and Saturday off, and local SIMs arrive in 7 days. The first swap day is Tue 3 Nov 2026. Five days of 5 swaps run on 3, 4, 5, 8 and 9 Nov, so the last swap day is Mon 9 Nov 2026.
- The prefilled rows in the tool show every status: two over the limit, five crossing soon, three inside, one local and one unknown.
How to read the results
- The action list. SIMs over the limit or crossing it inside the warning window. This is the list the CSV export carries.
- Next deadline. The nearest date a SIM that is still inside the limit will cross it.
- Swap plan verdict. Ready when every SIM is swapped before its deadline. Check when more capacity fixes it. Stop when some deadlines pass before the first local SIM can arrive.
- Review age. How long ago you last compared the period with the official text. Over 90 days, check again.
Common mistakes with SIM dates
- Using the purchase date. A SIM bought in March and activated in July starts its count in July.
- Forgetting spare devices. A device in the store with an active SIM counts too. Add it to the list.
- Keeping the shipped period unchecked. Open the source link and compare. Update the last-checked date when you do.
- Swapping the SIM and not the settings. A new SIM usually needs new APN settings. Plan the configuration with the visit.
- Treating unknown as local. Check the origin with your SIM provider. The tool gives unknown SIMs no clock.
Assumptions and limits
The tool does arithmetic on the dates and rules you enter. It does not read your SIM provider's records, and it does not know the consequences of passing the period. It is not legal advice and does not say that any device, SIM or provider is approved or compliant. Other countries have their own rules. The period, the counting and the scope can change, so keep the last-checked date current.