When it comes to automated dialling, Ofcom sets strict rules, and getting them wrong can cost you dearly.
The regulations can be confusing for contact centre managers to digest because:
- They have gone through years of iterations and amendments.
- There is no single source of truth – there isn’t a complete version of all the regulations in one place.
That’s why we’ve put together this straightforward guide to help contact centres stay compliant. We’ve also included direct references to relevant Ofcom and ICO documentation to support your understanding.
Why it matters
Ignorance of the rules isn’t a defence. In 2018 alone, contact centres were fined more than £3 million for non-compliance. Whether you’re using predictive dialling, answer machine detection (AMD), or rotating CLIs, it’s essential to know exactly what’s allowed and what’s not.
Terminology you need to know:
ACS: Automated Calling System (also known as Automated Dialler Systems)
Abandoned call: An inbound call dropped before an agent is connected. Or, an outbound call that is disconnected by the recipient before it is connected to an agent.
Connect: A live call passed to an agent
AMD: Answer Machine Detection is a dialler feature that detects whether a call is answered by a person or voicemail, helping automate call handling and improve agent efficiency.
Silent calls: Silent calls happen when someone answers the phone but hears no one on the other end. They are a major cause of consumer complaints and a red flag for regulators. Silent calls have three common causes:
- False positives: The system mistakes a live person for an answering machine. This can happen when using Answer Machine Detection.
- Abandoned calls with no message: The system hangs up instead of leaving a recorded message.
- Agent issues: A call is connected, but the agent is muted or doesn’t speak.
Ofcom treats all these cases seriously. Even unintentional silent calls can lead to penalties.
The 3% drop rate myth
Back in 2010, Ofcom said companies “should ensure their abandoned call rate is less than 3% of all live calls.”
That figure was often misunderstood as a formal rule, but according to Ofcom, it was neither a rule nor binding guidance. It was shared as a general reference point, not a compliance threshold.
At face value, 3% seemed straightforward: under 3% equals compliant, over 3% equals non-compliant. But that’s not how Ofcom intended it.
Why the clarification?
The issue is less about percentages and more about harm. A 5% drop rate in a tiny contact centre might mean just one missed call; a low risk. But a 0.5% drop rate in a massive operation could mean tens of thousands of abandoned calls; which is a much bigger issue.
That’s why Ofcom later clarified that all contact centres should aim for 0% abandoned calls. It’s about limiting harm, not just hitting a number.
The misconception continues
Despite Ofcom’s clarification, many contact centres, and even some dialler vendors, still operate under the mistaken belief that up to 3% abandoned calls are acceptable. This misconception is risky, especially when suppliers advertise compliance under outdated assumptions.
Key takeaway: You can face scrutiny or enforcement action even if your drop rate is “low” on paper. It’s the harm that matters, not the percentage.
How MaxContact helps
This is exactly why we developed our un-droppable algorithm that supports both progressive and predictive dialling. It’s designed to help contact centres stay compliant with Ofcom’s 0% expectation, even in complex blended environments.
Reference: See Ofcom guidance, Section A4.12
How to calculate drop call rates correctly
It’s not enough to aim for a low drop rate to stay compliant. You also need to measure it correctly. Unfortunately, many contact centre systems still use the wrong formula to calculate drop call rates, either by mistake or to artificially deflate the numbers.
The only acceptable formula
Ofcom is clear on how drop rates should be calculated:
Drop Rate = Drops ÷ (Drops + Connects)
That means only predictive or automated call outcomes should be included, no inbound or manual dials should be included in the calculation. This is because including inbound and manual dials misrepresents your true abandonment rate, and can land you in regulatory trouble.
A common compliance pitfall
Some platforms (whether intentionally or not) include inbound calls or manual dials to dilute the drop rate. This practice is non-compliant and can give a false sense of security.
Key takeaway: To see how you’re currently calculating drop call rates, check your reporting system. If it allows you to include non-predictive activity in the drop rate calculation, it’s time to re-evaluate.
Reference: Ofcom Section A3.8 – with examples for Answer Machine Detection (AMD) both on and off
15-second minimum ring time rule
The 15 second ring rule stipulates that you have to call a number for a minimum of 15s before disconnecting as a no answer. This was introduced to stop nuisance tactics like “pinging”.
What is pinging?
This outdated tactic involved diallers ringing numbers for 1–2 seconds to detect if a line was live. The next day, agents would redial the “live” lines. You can imagine how annoying this was for customers and why it often resulted in frustrated or confused recipients.
There’s more to it than stopping gaming tactics. Like the rules around silent calls, this one is about preventing harm. People deserve a fair chance to answer their phone, and they shouldn’t feel anxious about missing a call because it rang for only a second or two.
Ofcom cracked down hard on this practice.
What you need to know
- Minimum ring time: All outbound calls made via ACS (automated calling systems) must ring for at least 15 seconds.
- Exception: The rule is less clear when it comes to preview call dialling; automated dials that behave more like manual ones. Some argue these aren’t subject to the 15-second rule, but Ofcom has not definitively resolved this.
Reference: See Section A2.15 of the Ofcom guidance
Rotating CLI: What’s allowed and what isn’t
Not long ago, there was a trend for calling line identification (CLI) calls to display local numbers. The system would present a Manchester number when calling a Manchester number, a Newcastle number when calling a Newcastle number, and so on.
Why was it popular?
This was a popular tactic to boost connect rates, and it worked pretty well. It also rotated the numbers, so people didn’t recognise you. Rotating numbers like this made calls seem local and more likely to be answered.
Why is it a problem?
Unfortunately, rotating numbers had an unintentional side effect. By displaying 100+ different numbers, it became nearly impossible for Ofcom or the ICO to trace complaints back to a single contact centre.
Complaints to a single number were low even when complaints about the call centre as a whole might have been very high. Therefore, this approach was seen as a way for contact centres to avoid investigation.
Key rule: Carriers are no longer allowed to rotate CLIs automatically or manually without a valid reason. And as of 29 January 2025, Ofcom now prohibits the use of UK-style CLIs on calls originating from outside the UK. Any CLI should be accurate and geographically appropriate.
What’s a valid reason to rotate CLIs?
In some circumstances, you can still present different numbers. For example, a well-established car dealership with branches around the UK, but a central call centre, can present a local dealer’s number – as long as those numbers are clearly associated with your business and you have a legitimate interest.
Another valid example is if return calls need to go to different departments, such as having one number for your returns department, another for marketing, and a different one for support.
Key takeaway: Make sure your CLI strategy is transparent, consistent, and traceable.
For more, see the Ofcom regulations, Section A1.20 – A1.23
Read our blog to learn more about CLI compliance.
Call blocking from carriers
Even if you’re Ofcom-compliant, you could still find your calls blocked. Not by regulators, but by mobile network carriers such as EE, Vodafone, O2, or BT.
Why does this happen?
Network carriers have a shared database and automated systems to detect and block what they perceive to be nuisance or low-value calls. This is based on:
- Connect rate or ASR (Answer Seizure Ratio): If your connect rate to Vodafone (for example) is low then Vodafone will interpret this as people not wanting to talk to you.
- Low ACD (Average call duration): If calls last less than 30 seconds, carriers may view them as unproductive or unwanted.
These signals can result in your CLI being automatically blocked across multiple network carriers.
From early 2025, UK network carriers must automatically block incoming calls that spoof UK numbers, particularly those originating from abroad. This adds to the existing measures where carriers use call patterns, such as low ASR or short ACD, to detect and block perceived nuisance traffic.
How to avoid being blocked
- Monitor ASR and ACD and continuously optimise these KPIs
- Leave voicemail messages to increase call duration and show positive intent
- Vary your call strategies, for example; consider preview dialling or callbacks to boost engagement
What to do if you’re blocked
- Change your outbound number.
- Raise a complaint with the termination carrier.
- Review your calling patterns and fix any root issues.
Unfortunately, as Ofcom makes clear, this blocking policy is actively encouraged:
Page 4 Formal Blocking Directions
Page 5 – Strategic Working Group (Ofcom confirms the SWG has blocked a large number of nuisance calls since its formation) Page 6 – Technical Measures (Ofcom forms Strategic Working Group)
Answer Machine Detection (AMD): Use it wisely
There’s a lot of controversy around AMD use. While it improves efficiency, it’s also a cause of silent calls when not used correctly.
What’s the risk?
Poor quality AMD systems can often mistake live people as answering machines, which ultimately leads to silent calls.
This is because when the system thinks a live person is an answering machine, no message is played and the call is not passed to an agent. These false positives are classed as silent calls and can result in regulatory penalties.
Is AMD banned?
No. Ofcom hasn’t banned AMD. That’s because when it’s configured properly, it has the potential to double agent productivity. However, it must be used in a way that minimises false positives and protects the customer experience.
Key takeaway: Always play a message if a call is dropped due to suspected AMD.
Reference: Ofcom Section 4.41
Two second CPA rule
CPA stands for Call Progress Analysis and is part of the AMD function. Two seconds is the amount of time your CPA is given to determine whether the called party is an answering machine or a live person.
Why it matters
Many dialler providers argue that two seconds isn’t enough and, as a result, suggest disabling AMD altogether. However, Ofcom’s stance is clear; if your system can’t decide within two seconds, the call must be passed to an agent to remain compliant.
Key takeaways
- Don’t be tempted to hold the call beyond two seconds to improve detection accuracy
- If you’re unsure, route the call to a live agent
- Avoid vendors that recommend longer analysis time or suppressing calls
At MaxContact, we work compliantly. If detection is inconclusive after two seconds, we pass the call to an agent.
For more, see Section A2.19 of the regulations.
Leaving messages to combat silent calls
Silent calls (when someone answers the phone only to be met with silence from the other end) are a top priority for Ofcom. One of the most effective ways to reduce silent call complaints is to leave an answerphone message.
Considerations
- Leaving messages can increase voicemail volumes. But on the other hand, it also protects your contact centre from regulatory risk
- Choose your voicemail messaging carefully. Be clear, concise and compliant with Ofcom guidance
Key guidelines for drop call messages:
- The message must be played within two seconds of the call being answered.
- It must identify your organisation by name.
- It should explain that the call was made by an automated system and apologise for the inconvenience.
- It must not include any marketing content or suggest the recipient calls back.
For more, see Section A1.6, A2.16
Automatic system recalls: Know the waiting rules
Once a call is dropped or sent to voicemail, you can’t just call back immediately. Ofcom sets strict rules around when and how numbers can be redialled.
Redial restrictions
- You are not allowed to call previous dropped calls within 72 hours, unless the next attempt is made by a live operator rather than a dialler system
- If voicemail is detected, you must wait until the next day to call again. Note that this means after midnight, not 24 hours.
These set waiting periods exist to stop aggressive redialling patterns that can be perceived as harassment.
How MaxContact helps
This is one of the reasons MaxContact has mixed-mode dialling, which means we can automatically move records from “predictive” to “preview” and back again.
Compliance tip: If your dialler doesn’t manage recall delays automatically, your agents could unknowingly break the rules.
Reference – Section A2.9
Harassment: A grey area you shouldn’t ignore
Ofcom doesn’t clearly define what constitutes “harassment,” which means it’s open to interpretation. Which is part of the problem. The guidance frequently uses the term “a reasonable amount”, which is difficult to implement in practice.
While this needs Ofcom clarification, we can make some assumptions as to what is meant by “reasonable amount”.
What does “reasonable” mean?
Context plays a big part, as it could depend on:
- The purpose of the call (e.g. debt collection that has a valid reason for calling vs. sales)
- The frequency of contact – how much is too much?
- The consumer’s previous interactions or expressed preferences
While there’s no universal call limit, the Financial Conduct Authority (FCA) has occasionally issued informal agreements allowing, for example, no more than X calls per day or Y calls per week. The Data & Marketing Association (DMA) also provides similar best practice guidelines using the OfCom and ICO Guidelines as a source.
Best practice for contact centres
- Monitor call attempt volume by channel and time frame.
- Log and honour consumer Do Not Call requests or call-back preferences.
- Introduce campaign-specific limits based on purpose (sales, service, collections).
- Use self-service tools to give customers more control.
Top tip: When in doubt, dial down frequency and focus on message quality.
While there’s no fixed legal limit on maximum attempts per customer, excessive calling can quickly cross into harassment. Common sense and customer sensitivity should guide your strategy, especially for outbound campaigns or debt recovery.
Do not call (DNC) lists: Good practice, not just compliance
Do you need a do not call list? It’s not in any regulations, but Ofcom and the ICO both expect contact centres to give customers a clear option to opt out of future contact. So, it’s good practice to have one.
People should be able to remove themselves from calling lists either by:
- Speaking to an agent
- Through self-service options such as IVRs or SMS
Top tip: Keep your DNC list updated in real time to avoid accidental re-dials.
Reference: Ofcom Section A1.25
TPS: Non-negotiable compliance
If you’re not checking your outbound data against the Telephone Preference Service (TPS) or Corporate TPS (CTPS), you’ve got a problem. TPS compliance is mandatory under UK law, and it’s enforced by the ICO.
Why it matters
The ICO has taken over enforcement of this regulation and doesn’t pull punches. Many recent fines have stemmed from TPS breaches, and non-compliance is easy to prove.
What’s required
You must screen your call lists at least every 28 days. Even if your data supplier claims to screen for TPS, it’s your legal responsibility to ensure it’s done correctly.
Best practice
- Spot-check all data against TPS/CTPS before dialling
- Regularly validate that your data provider is screening properly
- Ensure your dialler automatically blocks flagged numbers
When TPS screening is not required
TPS screening applies to marketing calls. If your call is not for marketing purposes, you may not need to screen:
- Non-marketing calls: Service messages, customer service updates, or market research are typically exempt.
- Debt collection: If you have a legitimate interest, such as recovering debt, calls may be exempt.
- Prior consent: If a customer has explicitly opted in, you can contact them even if they are on TPS or CTPS.
- Service-related calls: Notifications from banks, utility companies, or insurers aren’t considered marketing and don’t require TPS screening.
References:
Ofcom Section A1.25
TPS website
ICO website
The good news for the industry?
According to Ofcom, complaints about silent and nuisance calls have decreased in recent years. That’s a win for the industry, but it’s no reason to get complacent.
The regulatory environment remains strict, and enforcement is very much active. Contact centres that don’t keep up with changing guidance or fail to invest in compliant dialling strategies remain at risk of fines, reputation damage, or carrier blocking.
MaxContact helps contact centres stay compliant
MaxContact is your friend here. Our advanced contact centre platform is built with compliance at the core.
- Customisable suppression logic to enforce DNC and TPS exclusions
- Un-droppable algorithm to reduce abandoned calls
- Smart AMD handling to minimise silent calls
- Mixed-mode dialling to support compliant redials
- Real-time analytics to monitor drop rates and answer durations
Struggling to navigate the rules?
Speak to one of our experts or book a demo to see how we can help your contact centre stay compliant and competitive.
