Ofcom requires call centres and businesses running automated dialling systems to cap abandoned calls at 3% of live calls per campaign every 24 hours, ring unanswered numbers for at least 15 seconds, and stay silent for 72 hours before recontacting anyone left with a dead-air call. Add PECR consent duties for marketing calls and valid Calling Line Identification, and you have the core compliance framework Ofcom and the ICO both enforce.
TL;DR:
- Calls must be answered for at least 15 seconds and include an identification message within two seconds if abandoned, with a maximum 3% abandonment rate per campaign.
- Recontacting numbers is prohibited within 72 hours unless a live agent will handle the call, and abandoned calls are calculated per campaign or call center, not overall.
- Every call must carry a valid, dialable CLII, with strict verification needed when using VoIP or multiple carriers, and CLI spoofing risks increasing enforcement.
- Automated marketing calls require explicit prior consent, screening against TPS and CTPS, and transparent display of access and service charges on all platforms.
- Active management of dialers, real-time monitoring, and retention of compliance records for at least six months are essential to avoid Ofcom penalties and investigations.
Table of Contents
- Ofcom rules at a glance: the numeric thresholds and disclosure duties
- Abandoned and silent calls: definition, measurement and ACS controls
- Calling line identification: valid CLI, network numbers and spoofing controls
- PECR and marketing calls: consent rules, automated calls and TPS/CTPS obligations
- Operational compliance checklist: how to make an outbound programme Ofcom-proof
- Enforcement, penalties and what triggers investigation
- Balancing automation efficiency with regulatory safety
- A compliance-first way to handle answering without building it yourself
- Sources
- FAQ
Ofcom rules at a glance: the numeric thresholds and disclosure duties
Compliance officers juggling several regulatory documents tend to lose track of which figure applies where. Here's the full set in one place.
- Recontact rule: no repeat call to the same number within 72 hours unless a live agent is guaranteed.
- Information message timing: an abandoned call must trigger a recorded message within two seconds of answer, naming the caller and giving a dialable number.
- Record retention: keep evidence of compliance for a minimum of six months.
- CLI presentation: every call must carry a valid, dialable number under General Condition C6.
Separately, UK Calling governs cost transparency on 08, 09 and 118 numbers: callers must see the access charge (set by their own phone provider) and the service charge (set by whoever runs the number) shown together before they dial. If your business publishes an 0845 or 0871 support line, that pricing split has to be visible on your website and marketing material, not buried in the terms.
Abandoned and silent calls: definition, measurement and ACS controls
An abandoned call is one where the automated calling system (ACS) connects but disconnects before a human agent picks up, usually because more numbers were dialled than agents were free to take them. A silent call is the subset where the recipient hears nothing at all, no message, no tone, just dead air. Ofcom treats both as a form of persistent misuse of the network, and it's the category that draws the most enforcement attention because it directly distresses consumers.
The 3% rate is calculated per campaign or per call centre, not across your whole operation, so a badly tuned outbound run can breach the limit even while your overall numbers look fine. Crucially, you can't calculate around AMD errors: if your answer machine detection wrongly classifies a live human as voicemail and hangs up, that still counts as an abandoned call.
Three controls do most of the work in practice:
- Set conservative dialling ratios. Predictive diallers that overdial to compensate for no-answers are the single biggest cause of breaches.
- Tune AMD deliberately, not aggressively. A model tuned to minimise false positives will occasionally waste agent time on real voicemail. That trade-off is cheaper than a compliance breach.
- Guarantee live-agent escalation for any number the system has already abandoned once, so the 72 hour rule and the message requirement both have a fallback.
Pro Tip: *Run abandoned-rate reporting per hour, not per day.
Calling line identification: valid CLI, network numbers and spoofing controls
General Condition C6 requires that every call carries CLI data containing a valid, dialable telephone number. That sounds simple until you're running calls through a VoIP platform, a cloud contact centre, or an AI voice agent stitched together from three different carriers, at which point CLI can get dropped, malformed, or spoofed without anyone noticing until a call gets blocked.
Where CLI is missing or unreliable, ingress providers are expected to insert a network number, sometimes from ranges such as 08979, or block the call outright. That network-level filtering is increasingly aggressive, and Ofcom's own CLI authentication roadmap signals it's only getting stricter.
Three checks belong in every vendor review:
- Test outbound CLI presentation on real handsets across at least two networks before launch, not just in the platform's own dashboard.
- Get written assurance from your telephony provider that CLI is verified end to end, not just accepted at ingress.
- Monitor for a rise in dropped or unanswered calls that might signal silent network-level blocking rather than genuine no-answers.
PECR and marketing calls: consent rules, automated calls and TPS/CTPS obligations
The Privacy and Electronic Communications Regulations sit alongside Ofcom's rules and govern anything with a marketing purpose. Live marketing calls are generally permitted, but you must screen against the Telephone Preference Service and Corporate TPS before dialling, and claims management and pension calls carry extra restrictions on top of that baseline.
Automated marketing calls sit in a stricter category entirely: regulation 19 requires explicit prior consent from the recipient before you play them a pre-recorded marketing message. There's no soft-opt-out equivalent here the way there sometimes is for email.
- Screen every outbound list against TPS/CTPS and maintain your own internal do-not-call suppression list.
- Callers must identify their organisation and display a genuine contact number, never a withheld or invalid one.
- Record consent and any withdrawal of consent, and be able to produce that record if the ICO asks.
Operational compliance checklist: how to make an outbound programme Ofcom-proof
Most breaches trace back to a system left running unattended rather than a deliberate rule violation. Ofcom's own guidance is blunt about this: automated dialling technology needs active management, not set-and-forget deployment. Here's a practical build order.
- Build a live dashboard tracking abandoned-call rate, AMD false-positive estimates, and average ring time, refreshed hourly rather than daily.
- Set threshold alerts at 2% abandoned rate, well below the 3% ceiling, so a team can intervene before a breach registers.
- Staff for guaranteed-live-agent escalation on any number already flagged as abandoned, satisfying the 72 hour recontact rule without simply blacklisting the lead.
- Script the recorded information message so it names your organisation and a real, dialable number, and confirm it fires within two seconds of answer.
- Write CLI guarantees into vendor contracts, along with audit rights, incident response timelines and remediation service levels if CLI or AMD tuning drifts out of spec.
- Retain logs and configuration snapshots for six months minimum, covering dialler settings, AMD thresholds and abandoned-rate reports, not just call recordings.
Pro Tip: Treat vendor SLAs as compliance documents, not just performance contracts. A vendor that won't commit to a CLI-accuracy guarantee in writing is telling you something about how confident they are in their own platform.
A PECR-focused checklist is worth running alongside this one if your outbound programme includes any marketing element, since the consent and screening requirements sit on top of, not instead of, the abandoned-call rules above.
Enforcement, penalties and what triggers investigation
Ofcom investigates under its persistent misuse enforcement programme, using section 128 notification powers and fines that can reach into the millions for serious or repeated breaches.
- High complaint volumes from a single number range or campaign are the most common trigger.
- Abandoned or silent-call rates consistently above 3%, or a pattern of invalid CLI, both draw attention faster than a one-off spike.
- Failure to produce six months of compliance records during an investigation is treated as an aggravating factor, not a neutral gap.
- Documented remediation, tightened AMD settings, revised dialling ratios, updated vendor contracts, genuinely reduces enforcement severity when things do go wrong.
Balancing automation efficiency with regulatory safety
The instinct with any new dialling or AI voice system is to push volume from day one. That's backwards. Run a conservative pilot first, measure your actual abandoned-call rate and AMD false-positive count against real traffic, then scale once the numbers hold steady under load, not just in a test environment. Tie vendor payment or renewal to compliance metrics, not just call volume, and get CLI accuracy verified before a campaign goes live rather than after the first complaint arrives.
— Ravi
A compliance-first way to handle answering without building it yourself
Most of the controls above, dashboard monitoring, AMD tuning, CLI verification, six-month log retention, are things a business has to build and maintain itself if it runs its own dialling infrastructure. Gmdautomation takes a different route: Your AI answers, qualifies and books, from £300 per month, is delivered as a managed service with the compliance groundwork already built in, so you're not assembling ring-time logic and abandoned-rate dashboards from scratch.
That means capacity-aware call routing, conservative AMD tuning, CLI management and audit logging come as part of the monthly subscription rather than a separate build project, with no upfront implementation cost. For lettings businesses managing arrears calls, Your AI credit controller for lettings, from £250 per month, applies the same compliance-first approach to a more sensitive calling context. If you'd rather pilot a managed, Ofcom-aware answering system than build one internally, request a demo through the services page and see how the routing and monitoring hold up against your own call volumes.
Sources
FAQ
What is the proper way to answer telephone calls under Ofcom rules?
There's no single script Ofcom mandates for live agents, but automated systems must ring for at least 15 seconds before disconnecting and play an identifying message within two seconds if the call is abandoned. The message must name your organisation and give a real, dialable number.
What are the Ofcom regulations on abandoned and silent calls?
Abandoned calls can't exceed 3% of live calls per campaign or call centre over any 24 hour period, calculated to include AMD false positives. Numbers that receive an abandoned call can't be recontacted for 72 hours unless a live agent is guaranteed.
Will someone know I'm abroad if they call me?
That depends on your phone provider's roaming settings rather than Ofcom's call answering rules, which govern how businesses dial out, not personal caller ID behaviour. Some networks display a roaming indicator automatically; check with your own provider for how your line handles it.
What enforcement powers does Ofcom have?
Ofcom can issue section 128 notifications and impose fines for persistent misuse of the network, including breaches of the abandoned-call threshold or CLI requirements. Investigations are typically triggered by complaint volumes, sustained high abandoned-call rates, or repeated CLI failures, and having six months of compliance records on hand materially affects the outcome.
Does Gmdautomation handle Ofcom and PECR compliance for me?
Gmdautomation's managed AI answering service builds capacity-aware routing, AMD tuning, CLI management and audit logging into the monthly subscription rather than leaving you to configure it. Pricing starts from £300 per month for Your AI answers, qualifies and books, with details available on request via the services page.