Reverse billing is a term describing the process of taking micro-payments from a mobile phone account in response to a keyword being texted to a shortcode number.

The level of payment is normally in the range of £1 to £5 but that can vary. At this level it is mostly used for acquiring ringtones and logos or premium information. Increasingly it is also being used for small donations to charity but is not ideal as the sum received includes VAT which is difficult to recover and a handling fee retained by the phone networks.

A shortcode has 4, 5 or 6 digits, most commonly 5, such as 87007 or 60608. The keyword texted in will determine the rest of the transaction. So you might see “Text CHARITY to 87007 to donate £5”.