MHDS Specification 5 defines the Invoice object.
| Attribute | Data Type | Description |
| INVOICE | String | Random alphanumeric ID; imported invoices’ IDs might be numeric |
| OFFICE | String | Office ID |
| USER | String | Therapist ID (references User object) |
| CLIENT | String | Client ID |
| ITEMS | String | Comma-delimited list of Item IDs |
| STAMP | String or Datetime | Date of issuance |
| RECEIPTS | String | Comma-delimited list of Receipt IDs (if applicable) |
| DUE | Float | Sum of items’ fees minus sum of receipts’ amounts |
| IMPORTED | String or Int | See S10.1 & S10.2 |