Best Pay As You Go SIM 2025: UK and Ireland Options Compared

Anyone who’s ever stared at a monthly phone bill has probably considered a Pay As You Go SIM — a freedom from contracts with no credit check. This guide compares the best PAYG options in Ireland and the UK, focusing on the fine print around credit expiry, hidden costs, and how to keep your number when you switch.

Top providers in Ireland: Lyca Mobile, Three, Tesco Mobile, Eir ·
Minimum top-up: €5–€10 ·
Typical data allowance: 5–20 GB per top-up ·
Top-up validity: 30 days to 12 months depending on provider

How Does Pay As You Go SIM Work?

What is Pay as you go?

A Pay As You Go SIM, also known as a prepaid SIM, lets you pay for credit or data bundles upfront rather than signing a long-term contract. There’s usually no credit check, and you’re not locked into a fixed monthly bill.

PAYG suits people who want full control over their spending and no commitment.

The way it works: you buy a SIM, top up with a minimum amount (typically €5–€10 in Ireland, £5–£10 in the UK), and then use that credit for calls, texts, and data. Each time you use something, the cost is deducted from your balance. Many providers now bundle a set amount of data, minutes, and texts that last 30 days, as MoneySuperMarket (a UK comparison site) notes. When the credit runs out or the bundle expires, you top up again—easy.

Unlike postpaid plans, where you use services first and get billed later, PAYG requires you to keep credit in your account. As Uswitch (a UK mobile comparison site) explains, major UK networks such as Three, O2, giffgaff, and VOXI all offer PAYG deals, each with different rate cards and bundle options.

The pattern: five key variables, one takeaway—expiry policies are the hidden cost. The lowest per‑GB rate doesn’t matter if your credit evaporates before you use it. For Irish buyers, Eir’s 12‑month validity is a standout, while Three Prepay offers data rollover that softens the blow of short expiry windows.

If you’re on Three, you might find the Three Mobile Top Up guide useful for managing your credit.

Which Is the Best Pay As You Go SIM?

What is the best prepaid SIM card in Ireland?

Four networks dominate the Irish PAYG market: Lyca Mobile, Three Prepay, Tesco Mobile, and Eir. Each offers a slightly different trade-off between price, perks, and expiry policies.

The best choice depends on your data needs, coverage, and whether you value extras like Clubcard points or concert pre‑sales.

Here’s a side-by-side comparison of the main Irish PAYG options, updated for 2025:

The table below shows how each provider stacks up on key metrics.

The implication: Lyca Mobile offers the lowest entry cost, while Eir provides the longest validity. Your choice should align with how often you top up.

Who has the cheapest SIM plan?

In the UK, the answer changes frequently as providers compete on price. According to MoneySavingExpert’s latest guide, Talk Home is the cheapest PAYG SIM overall, charging just 1p per minute, 1p per text, and 1p per MB of data. That means a casual user paying £10 per year could be getting great value—but the network relies on O2’s infrastructure, so coverage is broad.

For a balanced bundle deal, MoneySavingExpert recommends Lebara (using Vodafone’s network), which offers 3GB of data, 300 minutes, and unlimited texts for an effective cost of about £2.84 per month over 12 months. That’s hard to beat if you want a set allowance rather than paying per MB.

What is the cheapest pay as you go SIM?

In Ireland, Lyca Mobile typically undercuts the competition on pure price. Its €5 top‑up unlocks a bundle with a few GB of data and unlimited calls, and the credit lasts 6 months. For even lower data usage, Three’s PAYG pay‑per‑use rates are 35p per minute, 15p per text, and 10p per MB, as reported by MoneySavingExpert—but those rates add up fast if you use data.

Three also gives PAYG customers a free 150MB of data for 48 hours every time they top up, according to MoneySuperMarket, which can be a lifesaver for light users who just need occasional connectivity.

What is the cheapest SIM card in Ireland?

For the absolute cheapest SIM, consider the per‑GB rates. Lyca Mobile’s €10 for 20GB works out at €0.50 per GB—among the lowest for PAYG in Ireland. Tesco Mobile’s €10 SIM‑only plan for the first 6 months gives you a solid data allowance with the added bonus of Clubcard points on every top‑up. But for pure low cost, compare the top‑up minimums: Eir’s €10 minimum is higher than Lyca’s €5, but its credit lasts 12 months, making it a better deal if you top up infrequently.

What Are the Disadvantages of Pay As You Go?

The expiry problem

The biggest trap with PAYG is credit expiry. Unlike bank accounts where your money stays put, mobile credit has a shelf life. MoneySavingExpert warns that many PAYG SIMs require occasional top‑ups to remain active. If you don’t top up within a set period, your credit disappears and you could even lose your number. For example, 1pMobile requires a £10 top‑up every four months, or you might be disconnected.

Higher per‑GB data costs

Data‑only bundles on PAYG can be more expensive per gigabyte than contract plans. MoneySuperMarket notes that Three’s PAYG rates are 35p per minute, 15p per text, and 10p per MB—which translates to €100 per GB if you pay per MB rather than buying a bundle. That’s a huge premium over bundle pricing.

No device subsidies

With PAYG, there’s no “free” phone. You buy the SIM and bring your own device. If you’re someone who likes getting a new flagship phone every two years without upfront cost, a postpaid contract with device subsidy might actually work out cheaper—even including the interest component. MoneySavingExpert notes that PAYG is best for people who already own their phone outright.

Roaming limitations

While EU roaming is generally included (roam like at home), roaming outside the EU can be costly. Some PAYG bundles don’t include roaming data, so you’d need to buy separate add‑ons or face steep per‑MB charges. MoneySuperMarket advises checking the provider’s roaming policy before travelling, as PAYG deals often have less favourable roaming terms than postpaid plans.

Can I Keep My Number with a Pay As You Go SIM?

Yes, and it’s free. Number portability is a standard right for mobile users in both Ireland and the UK. ComReg (the Irish communications regulator) requires all providers to support number porting, and the process is straightforward.

Number portability must be provided within 24 hours of request.

To keep your number, request a PAC (Porting Authorisation Code) from your current provider. In the UK, this must be provided within 24 hours of your request, as confirmed by Ofcom (the UK communications regulator). In Ireland, the process is similar. Give the PAC to your new PAYG provider, and the port usually completes within 24 hours.

Important: don’t cancel your old SIM before porting. The porting process automatically cancels the old contract. As MoneySavingExpert explains, if you cancel first, you lose your number before the new provider can take it over.

Is There a UK Pay As You Go SIM That Doesn’t Expire?

What is the 3 € 20 plan?

Some UK PAYG SIMs offer indefinite validity if you top up at least once a year. MoneySavingExpert’s guide notes that ASDA Mobile and Giffgaff have limited‑expiry policies, though Giffgaff’s goodybag expiration varies by plan. However, most UK providers—including Three UK—require a top‑up every 90 days to keep credit alive.

The “3 € 20 plan” is an Irish offer from Three that gives 60GB of data and unlimited minutes for €20 per month on a 30‑day rolling basis. It’s not a no‑expiry SIM—it’s a standard 30‑day bundle that automatically renews if you keep topping up. Similar offers exist in the UK, but always check the fair‑use policy for expiry terms.

For UK users seeking a true no‑expiry option, the landscape has narrowed. As MoneySavingExpert notes, a few providers still offer indefinite credit validity, but many have switched to shorter windows. The safest approach: pick a provider with at least 6‑month validity and set a calendar reminder to top up before the deadline.

Related reading: Three Mobile Top Up: Online, Phone & Prepaid Guide · Is Three Network Down Today Ireland? Live Status & Map

For a detailed comparison of prepaid SIM card options in Ireland, including the cheapest plans and network coverage, check out our dedicated guide.

Frequently asked questions