GSM codes for call forwarding: the complete overview

How the codes work

The codes are part of the GSM network standard (technically: MMI codes) and are executed by the mobile network, not by the handset. That is why they work the same way on every device and with every German network operator: type the code into the phone app, replace <target number> with the number calls should be forwarded to, press the call button. The network answers with a confirmation message on the display. What call forwarding is in the first place and what the alternatives are is explained in "Setting up call forwarding: the four routes and their pitfalls".

The reference table

The status check (*#, code, #) is defined in the same standard as activating and switching off (3GPP TS 22.030), and Telekom lists it in its help pages (example: *#67#). Not every provider documents it: the 1&1 help centre names only activating and deactivating (as of 2026-11-02). If no answer or an implausible one comes back, a test call from a second phone shows where the call ends up.

On the delay for no answer: <seconds> accepts values from 5 to 30 in steps of 5. So **61*<target number>**25# means: after 25 seconds of ringing, the call is forwarded. With no value given, the network applies a default. Practical value for businesses: 20–25 seconds — long enough to pick up yourself, short enough that callers do not hang up.

Activate, deactivate, clear — the difference

Three prefixes control what happens:

1. ** sets up and activates — the target number is stored.
2. ## deactivates and clears the forwarding rule in question.
3. *# only checks the status, without changing anything.

If you have lost track, dial ##002# — the catch-all clears every forwarding rule, and you can then set things up cleanly from scratch. Note: on a mobile, voicemail is itself a forwarding on no answer. The new forwarding replaces it, and ##002# deletes it too — to get voicemail back, set its forwarding up again.

Codes or the customer portal — when to use which?

The guides for each provider are separate articles: "Setting up call forwarding at Telekom", "Setting up call forwarding at Vodafone", "Setting up call forwarding with o2", "Setting up call forwarding with 1&1" and "Setting up call forwarding on the FRITZ!Box".

Pitfalls: what the codes cannot do

Landline: the two-star codes in the table are mobile codes and do not apply on a landline connection. Telekom and Vodafone do, however, document landline codes of their own with one star: *21*<target number># switches forwarding of all calls on, #21# switches it off again; Vodafone also lists *61* (no answer), *67* (busy) and, for cable connections, *62*. The details are in the guides to call forwarding at Telekom and call forwarding at Vodafone. Besides that, there are Telekom's Telefoniecenter, the 1&1 Control-Center or the router.

Caller ID (CLIP): because the mobile network carries out the forwarding, the standard has the forwarding destination receive the original caller's number, unless the caller withholds it (3GPP TS 22.081). Your own number arriving there, the CLIP problem, typically happens when a FRITZ!Box or phone system forwards the call itself. A test call from a second phone shows what arrives. Details in the article "Why the AI sometimes sees the wrong number (the CLIP problem)".

Cost: the forwarded leg of the call is paid by the line owner. At Telekom, forwarding on mobile costs the same as a normal call on the tariff. At o2, forwarding to other German mobile networks and to landlines costs €0.29 per minute even on tariffs such as O2 Free Unlimited (price list, as of 2026-07-08) — so there the flat rate does not automatically cover it. 1&1 states that additional connection charges may apply. Check your tariff and price list before you forward permanently.

Outliers: some tariffs restrict forwarding. On o2 Prepaid, call forwarding is possible only to the mailbox (price list, as of July 2026); 1&1 does not allow forwarding to foreign numbers on mobile. When in doubt, your own provider's help page is what counts.

What it is all for: the most common use case

The classic reason for these codes today is replacing voicemail: delayed forwarding to an AI phone assistant that picks up when you cannot. At scoco.ai that is exactly the standard route — you keep your number, one code per forwarding type is enough (the planner in the dashboard fills in your scoco number and the ring time for you), basic setup takes about 10 minutes. When a caller number is transmitted, the assistant offers to use it as the callback number — if the caller accepts, it is taken without being read back; with a CLIP problem, that is your own. A dictated number it reads back digit by digit. Hence the test call from a second phone.