Before you start

The passport you entered on, for SIM registration and for customs device registration
An unlocked handset and its IMEI number, from *#06#
Your entry stamp or e-visa, needed for the customs registration
Address proof and usually a KITAS for a home fibre contract or a postpaid line

Step-by-step

1
Buy the SIM at an operator store or mall counter
Telkomsel GraPARI, Indosat, XLSMART and Tri all have staffed outlets in Surabaya's malls. Juanda airport counters carry the usual premium. Bring your passport so the clerk completes registration on the spot — that is the reliable way to make sure the number is registered to you.
In personWho: You15–20 minutes; live within the hourA generous monthly package is a low six-figure rupiah sum in town
2
Register the SIM against your passport and verify it
Registration is compulsory; an unregistered line does not activate. There is a cap on lines per identity per operator, so do not let a shop register spare numbers against your passport to clear stock. Ask to see confirmation that the number is registered to your details before leaving.
In personWho: You, with the store filing itImmediate
3
Register your handset's IMEI at customs on arrival
A foreign-bought phone works for roughly 90 days and is then blocked at device level. Register at the Bea Cukai desk in the arrivals hall — free below a value threshold, and much cheaper than doing it later when duty on the full value can be assessed. If you land at Juanda, do it before leaving the terminal.
In personWho: You, at airport customsAbout 30 minutes on arrivalFree below the threshold; import duty above it or if late
4
Arrange home internet around the building or the housing cluster
In a landed house in one of the western or eastern clusters, IndiHome, Biznet, MyRepublic and others compete and installation takes days to a couple of weeks. In an apartment tower, whichever providers negotiated access are the only options and management may not admit another. Ask before signing, not after, and get the advertised speed in writing.
In personWho: You, with the developer's estate management or the providerDays to weeksRoughly IDR 300,000–700,000 a month for a workable package
5
Keep a data SIM on a second network if you work from home
Fibre outages and wet-season power cuts both take the router down. A cheap data-only SIM on a different operator, kept topped up, means an outage costs you five minutes rather than a day. This is standard practice among people who work remotely here.
Mobile appWho: YouInexpensive

Documents you’ll need

Passport photo page, for SIM registration and customs device registration
Entry stamp or e-visa, for the IMEI registration
Handset IMEI from *#06#
KITAS and address proof, for postpaid lines or a home fibre contract

Things most newcomers don’t know

The 90-day cut-off is tied to your handset, so a new SIM will not fix a dead phone.

Indonesia blocks unregistered foreign devices at the IMEI level. It presents as the phone losing all networks around the three-month mark, and the instinctive response — buy another SIM — fails identically. The remedy is customs registration of the device, free on arrival and potentially expensive later.

Source: Bea Cukai (Indonesian Customs) IMEI registration

The Telkomsel premium that makes sense in Bali does not obviously make sense in Surabaya.

Telkomsel's advantage is reach into rural areas, ferries and outer islands, which is why every Bali guide recommends it. Greater Surabaya is densely covered by all four operators, so the differentiator is package pricing and whether your colleagues are on the same network. Paying the coverage premium for a life spent between Rungkut, Gresik and the western clusters buys you very little.

Source: Operator coverage maps; Indonesian market reporting

In an apartment tower, the fibre decision was made before you arrived.

Buildings are wired by whichever providers negotiated access, and management will not always let a competitor in. If working from home matters, the question 'which providers are live in this building and at what speed' belongs before the lease, not after. Landed houses in the housing clusters have genuine choice; towers frequently do not.

Source: Practitioner reporting; provider coverage maps

Do not let a shop put spare numbers on your passport.

One identity may register only a limited number of prepaid lines per operator. Shops sometimes register extra numbers against a customer to hit a target or clear stock, using up your allocation and leaving lines registered to you that you do not control. Verify what is on your passport before you walk out.

Source: Indonesian SIM registration rules (Komdigi)

Common mistakes to avoid

Assuming a foreign handset keeps working past three months without customs IMEI registration.
Registering the IMEI late and being assessed duty on the phone's full value.
Paying airport prices for a SIM when you could buy the same package in town the next day.
Signing an apartment lease without checking which fibre providers the building actually supports.
Letting a shop register additional lines under your passport and exhausting your per-operator allowance.

Some of this may be out of date. Spotted something inaccurate? Help us keep it right for the next newcomer.