How the UK OFCOM drop-rate calculation differs from the US

The core difference between US and UK drop-rate rules

In the US, the FTC's Safe Harbor rules define an Abandoned call as any call where a live person answers but is not connected to an agent within two seconds of the agent greeting. The Drop rate — the percentage of those calls — must stay at or below 3 percent per campaign.

UK Ofcom (UK) regulations share the same intent but differ in two meaningful ways: first, the drop rate can be calculated across all of a company's campaigns combined rather than per campaign; and second, since December 2015, OFCOM changed the formula for how dropped calls are counted.

The December 2015 OFCOM formula change

The pre-2015 method counted every abandoned live-person call in the drop-rate calculation. The December 2015 update introduced a formula that accounts for anticipated answering machine drops — specifically, the expected number of answering machine calls that would be abandoned given the rate at which agents are dispositioning calls as answering machines.

In plain terms: if your agents are flagging a predictable share of calls as answering machines, the formula acknowledges that some abandoned events are answering machines that the AMD (answering machine detection) system missed — not live people who were left waiting. Those anticipated machine-related drops are subtracted from the drop count, giving a more accurate picture of actual live-person abandonment.

The result is that operations with higher answering machine rates — typical in many B2C outbound verticals — get a fairer drop-rate number under OFCOM's December 2015 method than they would under the older calculation or under the US method.

How to enable the OFCOM drop calculation in VICIdial

flowchart TD
  A[Enable UK OFCOM Drop Calculation] --> B[Step 1: Admin - System Settings]
  B --> C[Enable UK OFCOM Drop Calculation toggle]
  A --> D[Step 2: Campaign Detail]
  D --> E[Enable UK OFCOM Drop Calculation per campaign]
  A --> F[Step 3: Answering Machine Statuses]
  F --> G[Set AM flag = Y on every AM status code]
  C --> H{Both enabled?}
  E --> H
  H -- Yes --> I[OFCOM Dec 2015 formula active]
  H -- No --> J[Standard drop calculation used]

This feature requires enabling in two separate places. If you only enable it in one, it does not activate — both must be turned on:

1. Admin > System Settings: Find the "UK OFCOM Drop Calculation" option and enable it. This is the system-level switch.
2. Campaign Detail: In each Campaign that should use the OFCOM method, find the "UK OFCOM Drop Calculation" option and enable it there too.
3. Answering Machine status flags: Every Status (lead status) code that agents use to disposition answering machine calls must have the Answering Machine flag set to Y. If any AM status is missing this flag, calls dispositioned with that code will not feed into the formula correctly, skewing the drop-rate calculation.

The multiple-campaign drop rate group

Alongside the OFCOM drop calculation, UK operations can also use the Multiple Campaign Drop Rate Group setting. Set all campaigns in a company to the same drop rate group and the drop percentage is calculated across all of them as a pool. This helps operations that have some lower-volume campaigns that might spike above the limit individually while the overall company rate stays well within it.

The two features are independent — you can use either, both, or neither. For most UK operations running multiple campaigns, using both makes sense: the December 2015 formula gives a fairer base number, and the grouped drop rate gives more flexibility across campaigns.

Where to go next

The 72-hour lockout for abandoned calls is a separate OFCOM requirement covered in the UK 72-hour drop-lockout rule. For the full UK and US compliance picture, see the VICIdial compliance overview.

If you want help getting these settings correctly configured for your UK campaigns, see our pricing and support options.