TP18T is a standard SAP Table which is used to store Business Partner: Description of Reason for Undesirablitiy data in SAP systems, such as SAP R/3, S/4HANA, depending on the version and release level.
The TP18T table consists of various fields, each holding specific information or linking keys about Business Partner: Description of Reason for Undesirablitiy data available in SAP. These include LANGU (Language Key), UNW_REASON (Reason for Undesirability), UNW_TEXT (Reason for Undesirability)... See below for full list along with technical details, documentation, text table, check tables, foreign key relationships, conversion routines, relevant tcodes and example ABAP select code etc. .