In e-invoice schema, for each field, ‘Cardinality’ is marked as 0..1 / 1..1 / 1..n / 0..n. This denotes whether a field is ‘mandatory’ and ‘repetitive.’
| Notation | Meaning |
|---|---|
| Starts with 0 | Optional field |
| Starts with 1 | Starts with 1 Mandatory field |
| Ends with 1 | Data for the field can be entered only once |
| Ends with n | Data for the field can be entered multiple times |