AMD and the UK OFCOM Drop Calculation: Changing the Math

If you dial UK numbers, the way your drop rate is calculated is not the same as it is in the US or Canada. Since December 2015, OFCOM (Ofcom (UK)) uses a formula that treats answering machines as a special case, and answering machine detection (AMD (answering machine detection)) is what makes that formula possible. Getting this right keeps your campaign on the safe side of UK abandonment rules.

What changed in 2015

The standard way to compute a Drop rate counts dropped calls against the total of answered calls plus drops. The OFCOM method adds a step before that division. It estimates how many of your drops were actually answering machines and removes that share from the drop count first, because abandoning a machine is not the same harm as abandoning a person.

It does that estimate using your agent-answered answering-machine percentage. It takes that percentage and subtracts it from the raw number of drops. The adjusted drop number is then divided by the total of agent-answered human calls plus the drops. The result is a Drop percentage limit that reflects only the calls a real person would have wanted to take.

flowchart TD
  A[Total drops] --> B[Estimate machine share from agent AM percent]
  B --> C[Subtract machine share from drops]
  C --> D[Adjusted drop count]
  D --> E[Divide by human answers plus drops]
  E --> F[OFCOM drop percentage]

Why AMD sits at the center of this

The formula leans on knowing how many machines you hit, and that number has to be trustworthy. For agent-statused answering machines to be counted properly, an answering machine status flag is used to gather those statuses. In other words, the calls your agents mark as machines feed the same calculation. If AMD is sloppy and an AMD false positive tags live people as machines, your abandonment math drifts off the truth in both directions.

This is also why clean dispositions matter. The Abandonment rate OFCOM cares about is only as accurate as the statuses behind it, so every Abandoned call and every machine Disposition needs to be recorded consistently across the campaign.

How to turn it on

The UK OFCOM Drop Calculation is not a single switch. It exists in two places: as a system-wide setting and as a per-campaign option, and both must be enabled before any campaign uses the new method. The campaign field defaults to 0 for inactive, so a fresh campaign will use the standard method until you change it.

1. Enable the OFCOM drop calculation at the system settings level first.
2. Open the campaign you dial UK leads on and switch its UK OFCOM Drop Calculation option to active.
3. Confirm AMD is running so the answering machine status flag has data to gather.

Because the formula depends on agent-marked machine statuses, AMD only helps here when it runs under an auto-dial method. AMD does nothing in MANUAL or INBOUND_MAN modes, so a UK campaign that relies on this calculation should be on a Ratio dialing or adaptive setup. The mechanics of switching AMD on are covered in our piece on setting up an AMD campaign.

Keep your math defensible

The OFCOM method only rewards you if detection is accurate, so it pays to read the full AMD and CPD complete guide and tune accordingly. If you want help keeping a UK campaign compliant and well tuned, see VICIfast pricing and we will set the system and campaign options up correctly for you.