Data types and formats

Numeric

A number, usually a whole, positive integer, but can also have decimals, f.ex. in case of money amounts (see below for more info on money amounts).

Integer

A whole, positive number, f.ex. 1 or 879613

String

Any sequence of characters (text) - i.e. letters, numbers and special symbols.

Boolean

A parameter that can only have one of two values, 0 or 1.
Usually, 0 roughly translates to "no" and 1 to "yes".

Date/time

Dates are always represented in the format YYYY-MM-DD and time HH:MM:SS. Date and time can be put together, separated by a single space.
Timezone is always CET - Central European Time, usually equivalent to UTC+1 or UTC+2 in summer (DST - Daylight Saving Time).

Money amounts

Money amounts are usually represented with 2 decimals, separated by a comma. The currency is always specified in a separate parameter.
No thousand separators or other symbols are included.

Country codes

Countries are specified in the 2-letter ISO 3166-1 alpha-2 format.

Language codes

Languages are specified in the 2-letter ISO 639-1 format.

Currency codes

Currencies are specified in the 3-letter ISO 4217 format.

Supported billing currencies (subject to restrictions by merchant location):