Conditional call forwarding: a UK setup guide

This is the setting that makes an overflow or out-of-hours service possible without porting your number or changing provider. It is worth understanding properly, because the difference between conditional and unconditional forwarding is the difference between a safety net and losing control of your line.

Conditional vs unconditional

• Unconditional forwarding sends every call straight on. Your phone never rings. This is almost never what a small business wants.
• Conditional forwarding sends a call on only when a specific condition is met: you did not answer within a set time, your line was busy, or your phone was unreachable. You keep first refusal on every call.

The three conditions

On UK mobile networks these are set separately, so you can enable one, two or all three.

• No answer — you did not pick up within the ring time (typically 15–30 seconds, sometimes adjustable).
• Busy — you were already on a call. This is the one that catches overflow.
• Unreachable — no signal, or the phone is off. The one that matters in basements and rural jobs.

Setting it up on a UK mobile

Every major UK network supports the standard GSM codes. Dial them from the handset whose calls you want forwarded, replacing NUMBER with the destination in full international format (for example 447700900123):

• No answer: **61*NUMBER# — then press call
• Busy: **67*NUMBER#
• Unreachable: **62*NUMBER#
• Turn each off: ##61#, ##67#, ##62#
• Check what is currently set: *#61#, *#67#, *#62#

Most handsets also expose these under Settings → Phone → Call Forwarding, though the settings app on some Android builds only offers a subset. The dial codes are the reliable route.

Landlines and VoIP

Dial codes do not apply the same way. On a VoIP or cloud phone system the equivalent is a call-flow or failover rule in the provider's admin portal — look for “forward on no answer”, “failover destination” or “call flow”. On a traditional landline, ask the provider directly; the feature is sometimes chargeable and sometimes not available on the tariff at all.

What it costs

The setting itself is free to enable on UK mobile networks. The forwarded leg — the call from your number onward to the destination — may be charged to you as an outbound call, depending on your tariff. On most business plans with inclusive UK minutes this is covered; on some pay-as-you-go and older tariffs it is not. Check with your provider before you enable it on a high-volume line. Do not accept a supplier telling you it is definitely free; they cannot see your tariff.

Checking it actually worked

The number of businesses that set this up and never verify it is remarkable. Two minutes:

• From a different phone, call your number and let it ring out without answering. It should land at the destination.
• Start a call on your phone, then ring your number from a third phone. That should land too, if you enabled the busy condition.
• Turn your phone off and call it. That tests unreachable.
• Finally, call and answer. It should reach you normally, with nothing forwarded. If it does not, you have set unconditional forwarding by mistake.

A note on order

Set up the destination first and test it, then enable forwarding. Doing it the other way round means live customer calls arrive somewhere that is not ready for them. If you are setting this up with us, forwarding is deliberately the last step — testing comes before it is enabled.