Data rollover in Belgium: who keeps your unused GB

No, almost never: your unused GB disappear on the first day of the next billing period. As of 13 October 2026, two Belgian brands are the exception, BASE on the Telenet network and UNDO on the Orange network. Rollover comes with limits, and it often matters less than the label you choose.

Does unused data carry over to the next month?

As a rule, no. A Belgian mobile plan sells a monthly allowance, and whatever remains on the last day of the billing period is lost. Mega says so on its help page: minutes, texts and data can only be used "during the billing period in which the plan is valid". The terms of hey!, on the same Orange network, fit in one line: remaining minutes, data and texts "are not carried over to the next month".

The waste is not trivial. The IBPT (BIPT), Belgium's telecom regulator, published an average usage of 11.9 GB per month per customer on 14 July 2026, while entry-level brands routinely sell 30 to 100 GB. UNDO did something rare in June 2026 by publishing its own customers' usage: 2.4 GB on average in May on the Zero Waste plan, or 60% of the 4 GB they pay for.

Which Belgian brands roll over unused data?

Two out of fourteen. And not on the same network.

In Belgium, only a handful of companies own a mobile network (Proximus, Orange, Telenet and the newcomer DIGI); every other brand either belongs to one of them or is an MVNO, a mobile virtual network operator that rents capacity from a host network.

"Not announced" means no public page we checked mentions rollover, which L'Avenir confirmed on 25 June 2026 when it wrote that most operators do not offer it. One Belgian comparison site contradicts itself: its news item of 19 August 2026 says Mobile Vikings rolls nothing over and presents BASE as the only brand that does, while its data-plan guide, updated on 7 October 2026, credits Mobile Vikings with rollover and leaves UNDO out. We keep the version recorded when Mobile Vikings launched its new plans, to be reconfirmed.

The telling case is on the Telenet network. BASE and Telenet belong to the same group and use the same antennas, yet only BASE rolls data over. The rule follows the label, never the signal.

How does BASE's Data Jump work?

Automatically, and only once. On BASE 15 (15 GB, €15), BASE 20 (50 GB, €20), BASE 29 (90 GB, €29) and BASE 39 (300 GB, €39), unused data moves to the next month with nothing to activate and no surcharge. BASE's help page sets two rules: carried-over volume is used before the month's own allowance, and it can only be carried over once.

Take a BASE 15 customer who uses 8 GB in October. November starts with 22 GB: 7 GB carried over plus the usual 15 GB. If they use only 5 GB in November, those 5 GB come out of the carried-over volume, the remaining 2 GB expire, and the untouched 15 GB of November move on to December in turn. The once-only rule therefore costs little, as long as usage does not collapse two months in a row.

Older BASE monthly plans do not get Data Jump: minutes, texts and data reset to the full allowance each month, and BASE suggests switching plans in My BASE. The idea is not new there. In September 2017, BASE already launched plans that carried minutes and gigabytes from one month to the next; now that calls are unlimited, only data rolls over.

On price, Selectra reports on 13 October 2026 a 30% discount for any sign-up before 16 November 2026, described as kept for the whole contract: BASE 15 would then cost €10.50. Get written confirmation that the discount does not stop after month twelve.

Does UNDO also roll over minutes and texts?

Yes, automatically and free of charge. UNDO, an independent MVNO on the Orange network, carries data, minutes and texts over to the next month across its range: Zero Waste (4 GB, €4), Rise (8 GB, €8), Grow (20 GB, €10), Boost (30 GB, €18) and Wild (40 GB, €24), prices checked by Selectra in October 2026, excluding promotions. Each extra gigabyte costs €1.

None of the pages we checked says whether carried-over volume expires after one month, as at BASE, or keeps adding up.

Is rollover worth more than the price gap between labels?

Rarely. To check, take an irregular user who alternates 8 GB and 20 GB months, 14 GB on average, just above the Belgian average. The question is simple: what is the cheapest plan that covers the 20 GB months without overage charges?

Month-13 prices, excluding temporary discounts. BASE: Selectra, checked 13 October 2026. Orange: month-13 price checked 29 September 2026. UNDO: Selectra, October 2026. hey!: plans page checked 5 October 2026. The coverage and annual cost columns are our calculations.

At BASE, rollover saves €60 a year: the gap between BASE 15 and BASE 20, which this profile would need without Data Jump. On the Orange network, hey! mobile M covers the same profile without any rollover, for €72 a year less than BASE 15. Even with the 30% discount, BASE 15 at €10.50 comes to €126 a year, €18 above hey!.

I would not pick a plan for its rollover. I would take it as a bonus when the label is already the cheapest for my volume, and that is seldom the case.

What should you do, depending on your usage?

Four things to check before counting on rollover

The rule sits in the price terms or the help pages, almost never on the home page.

• How many times data can roll over: once at BASE, nothing published at UNDO.
• The order of use: at BASE, carried-over volume goes first, which limits losses.
• Which plan is covered: an older BASE plan has no Data Jump, even at the same price.
• What happens to the balance when you leave: porting takes your number with you, not your remaining gigabytes.

We do not subscribe to any of these plans and measure nothing in the field: this page cross-checks the brands' help pages and public terms, the Belgian press and two comparison sites, consulted between 5 and 13 October 2026. Plans sorted by month-13 price, host network shown, are in our 5G plan ranking. To estimate your own needs, see how much data you really need on 5G; for the network behind each label, the brand-by-network table; and to switch brand without switching antennas, the step-by-step guide. Telecom consumer rights are summarised by the IBPT, and billing disputes go free of charge to the Ombudsman for Telecommunications.

Sources: IBPT, press release on mobile data usage, 14 July 2026, and consumer section; BASE, help page on carrying over minutes and data, checked 13 October 2026; Mega, help page "Can I carry over what I did not use to next month?", checked 13 October 2026; hey! Telecom, plan terms, July 2022 version, and mobile plans page checked 5 October 2026; Test Achats, "UNDO: des abonnements mobiles encore plus avantageux", 22 September 2026; Selectra, BASE mobile and UNDO pages, updated 12 and 13 October 2026; CallMePower, BASE mobile internet page (updated 7 October 2026), Mobile Vikings news item (19 August 2026) and data-plan guide (7 October 2026); L'Avenir, articles of 1 April, 25 June and 17 August 2026, and of 12 September 2017 on the launch of rollover at BASE. Official brand pages cited: BASE rollover help page and Mega help page. No link on this page is monetised.