Rate types

Reduced rate £84 (for travel to the US)

For travel in the lowest class of travel available on the plane for seat pitches less than 1.016 metres (40 inches).

Standard rate £185

For travel in any other class of travel or where the seat pitch is more than 1.016 metres (40 inches).

Upgrades

If a passenger pays to upgrade at any stage in the journey, then they’re travelling in the higher class.

The same applies to free upgrades if there’s an element of entitlement or priority not enjoyed by other standard class passengers. For example ‘perks’ enjoyed by airline employees.

A passenger remains in standard class if they get a free upgrade but has no expectation of, or entitlement to one.

https://www.gov.uk/guidance/rates-an...passenger-duty
An awkward use of "standard" as in standard rate / standard class, but there you go.


but yes, payment means payment in whatever form, whatever instrument is applied

There is a third rate of duty (£554), but that is intended for passengers carried on air taxis, corporate jets etc