Why mobile numbers outlast landlines in a B2B contact file
The fundamental difference between a mobile number and a landline in a B2B contact file is what ties the number to the world. A landline is tied to a physical location and an employer. A mobile number is tied to a person. When an Operations Director at a Sheffield manufacturer leaves for a competitor role in Leeds, the desk number she had is reassigned or disconnected within weeks. Her mobile number almost certainly stays the same.
That structural difference drives a measurable gap in decay rates. Business landlines in UK B2B files typically become invalid at 12-20% per year, depending on sector. Technology firms and agency businesses, where staff turnover is high and office consolidations are common, sit at the upper end of that range. Utilities and public-sector bodies, where headcount is more stable and offices rarely move, tend towards the lower end. In any case, a B2B file that is not refreshed for 18 months will have lost a fifth or more of its landline coverage to disconnection and reassignment.
Mobile numbers in the same file decay at 4-8% per year. The reasons for attrition are narrower: voluntary number change (rare, typically prompted by a desire to escape persistent callers), death, retirement, or emigration. Job-to-job portability is the key driver of the lower rate. Ofcom's number portability rules have made switching mobile provider while keeping your number straightforward since the early 2010s, so even a mid-career professional who has worked for five employers in a decade will often carry a single mobile number throughout.
This matters most for B2B files targeting decision-makers by name. A direct-dial mobile appended to a named contact record will still reach that person even if they have changed employer, whereas a landline is already dead. For B2B direct dial numbers in the UK, mobile availability is therefore a strong quality proxy: the higher the proportion of verified mobile numbers on a list, the longer its useful life before a cleanse cycle is needed.
Answer rate differences: what the numbers look like in practice
Decay rate tells you how long a number stays valid. Answer rate tells you how useful it is once it is dialled. These are separate questions, and the answer-rate picture for mobile versus landline is also clearly in mobile's favour.
For B2B campaigns, office landlines yield answer rates of 15-25% across a typical dial list. Much of that gap from 100% is explained by gatekeeping: calls to a main switchboard or a shared team number are screened, diverted to voicemail, or answered by a colleague who cannot help. Even direct-dial desk numbers are often diverted to voicemail during meetings or after-hours, and many professionals now decline calls from unknown fixed-line numbers out of habit. B2B mobile numbers, where verified at the named-contact level, achieve 25-35% answer rates. Senior contacts in particular (MDs, FDs, heads of department) are more likely to answer a mobile from an unfamiliar number than they are to return a voicemail left on a desk phone they rarely check.
For consumer campaigns, the gap is similar. Residential landlines typically see answer rates of 20-30%, but that figure has been falling for a decade as household landline penetration drops. Ofcom's 2025 Communications Market Report notes that 25% of UK adults live in mobile-only households, a figure that rises steeply among under-45s. Consumer mobiles deliver answer rates of 35-45% on a well-maintained, recently verified list.
In our experience, the single biggest driver of answer-rate variance is not number type but recency of verification. A mobile number verified in the last six months outperforms a landline verified three months ago. The lesson is that number type and verification age interact: always ask your data supplier when the numbers were last validated, not just what type they are.
Regulatory differences: TPS, CTPS, and Ofcom time-of-day rules
One area where mobile and landline are treated identically under UK law is suppression. The Privacy and Electronic Communications Regulations (PECR) give individuals and corporate subscribers the right to register with the Telephone Preference Service (TPS) and Corporate Telephone Preference Service (CTPS) respectively. Both registries cover all telephone numbers, including mobiles. A consumer who registers their 07x mobile with TPS must be treated the same as a consumer who registers a residential 01x number: neither can be called for direct marketing purposes without their prior consent.
Callers who assume mobile numbers are outside TPS jurisdiction face ICO enforcement action. The Information Commissioner's Office has fined organisations for exactly this misunderstanding. TPS and CTPS washing is mandatory for every outbound telemarketing campaign, regardless of whether the dial list consists of mobiles, landlines, or a mix of both. See the telemarketing data quality guide for a full account of pre-dial suppression requirements.
Where mobile and landline do diverge is in Ofcom's time-of-day guidance. Ofcom's persistent misuse rules and the DMA's best practice guidance both suggest calling consumers between 08:00 and 21:00, and corporate contacts during normal working hours (broadly 09:00 to 17:30). Calling a personal mobile number outside those windows is more likely to result in a complaint, because the recipient experiences the intrusion directly rather than having an office landline ring in an empty building. For corporate mobiles, calling at 07:45 or 19:30 is technically within the Ofcom window but is likely to generate a hostile response from a senior decision-maker who has already left the office for the day.
TPS applies to every number type
There is no mobile exemption under PECR. Any outbound telemarketing dial list, whether built from mobile numbers, landlines, or both, must be washed against TPS (consumer) or CTPS (corporate) within 28 days before use. Failure to do so is an ICO enforcement risk and the fine threshold is set at individual campaign level, not per number called.
Mobile vs landline: comparison table
The table below summarises the key quality dimensions across four scenarios. "B2B named contact" refers to a record tied to a specific individual at a company; "B2B role-based" refers to a number associated with a job function or department rather than a named person.
| Dimension | B2B mobile (named contact) | B2B landline (direct dial) | B2B landline (switchboard / role-based) | Consumer mobile | Consumer residential landline |
|---|---|---|---|---|---|
| Annual decay rate | 4-8% | 10-16% | 12-20% | 5-9% | 8-14% |
| Answer rate (typical) | 25-35% | 18-28% | 15-25% | 35-45% | 20-30% |
| Survives job change? | Yes (usually) | Rarely | No | Yes (usually) | No (house moves) |
| Call cost | Higher (07x rates) | Lower (01x/02x rates) | Lower (01x/02x rates) | Higher (07x rates) | Lower (01x/02x rates) |
| TPS/CTPS applicable? | Yes (CTPS) | Yes (CTPS) | Yes (CTPS) | Yes (TPS) | Yes (TPS) |
| Gatekeeper risk | Low | Low-medium | High | None | Low |
| Best for | High-seniority B2B, personal sales | Mid-seniority B2B, office-hours campaigns | Gatekeeper-first outreach, list building | Consumer products, personal finance, utilities | Older demographic targeting, regulated sectors |
When does landline still beat mobile?
Mobile has the better numbers on almost every quality dimension, but four scenarios consistently favour a verified landline over mobile.
Cold corporate B2B at large organisations
When the target is a procurement team at a FTSE 250 business or a Finance Director at an NHS trust, calling a personal mobile cold is often the wrong opening move. These contacts are accustomed to vendor calls being routed through proper channels, and an unexpected mobile call from an unknown number can register as intrusive before you have said anything. A direct-dial desk number, presented professionally, signals that you have done due diligence and are not working from a bulk-purchased consumer list. The answer rate may be slightly lower, but the quality of conversation when it connects tends to be better.
Structured working-hours campaigns
If a campaign is deliberately scheduled for 10:00 to 12:00 and 14:00 to 16:00 on working days (classic B2B dialling windows), a direct-dial landline is more likely to find the target at a desk and in a professional frame of mind than a mobile, which may ring on the school run, in a gym, or during a personal appointment. Time-windowed campaigns lose some of their precision when the number type is mobile.
Call cost at high volume
The 1-3 pence per minute premium for 07x numbers adds up fast. A campaign dialling 100,000 numbers per month at an average call duration of 3 minutes (including connects and non-connects) generates approximately 50,000 minutes of billable time on connects alone. At 2 pence per minute premium, that is £1,000 per month in additional termination costs, or £12,000 per year. For campaigns where landline coverage is solid, working through landlines first and using mobile as a fall-back reduces cost per conversation without meaningful sacrifice in answer rate.
Older consumer demographics
For B2C campaigns targeting over-65s, residential landline penetration remains high (above 75%), and answer rates for this demographic on landlines are competitive with mobile. Products covering funeral plans, stair lifts, equity release, and similar categories often achieve better results on landline for this age group. The same applies to any product where the call is expected to run long (insurance quotations, financial advice) and the recipient is more comfortable on a handset than a mobile.
Building a blended number strategy
The practical conclusion for most campaigns is not to choose one number type and ignore the other, but to use both with a defined priority order. A workable framework runs as follows.
First, identify which records in your file carry a verified mobile number at the named-contact level. These are your primary dial pool for senior decision-makers, personal sales, and any campaign where speed-to-connect matters. Prioritise these records in the first dial pass.
Second, for records with only a landline (direct dial or switchboard), schedule those contacts during the 10:00-12:00 and 14:00-16:00 windows when a desk answer is most likely. Use the switchboard number only as a last resort: a gatekeeper call to confirm the contact is still at the company and request a direct number is often more efficient than five unsuccessful switchboard attempts.
Third, run the entire dial list through TPS or CTPS suppression within 28 days before the campaign begins, covering both mobile and landline numbers on each record. A record with a TPS-registered mobile but a clean landline can still be dialled on the landline. The suppression check operates at the number level, not the record level.
Finally, build decay tracking into your campaign reporting. Every call outcome that produces a "number not recognised" or "number reassigned" result is a data point about your list's health. If more than 10% of your landline dials are returning invalid-number results, the file needs a cleanse. If mobile invalid rates creep above 6%, the same is true. These thresholds are lower than many callers expect, because invalid-number results slow agents down and degrade the conversation rate for the contacts who do answer.