UDF (Abbreviation)
UDF stands for User Defined Field, in German Custom Field. It refers to additional attributes that are attached to standard objects in SAP Business One, such as items, business partners, journal entries, or document rows, without the need for add-on development or a change release. UDFs are the central instrument for adapting B1 to industry- or company-specific requirements.
Context
User-defined functions are created using Extras → Customisation Tools → Custom Fields - Management. For each field, the name, description, data type (alphanumeric, numeric, date, checkbox) and length are defined; valid values, default values, and a Link to a UDT. Technically, UDFs are stored as additional columns with the prefix U inserted into the respective database table — for example OITM.U_VPS_DTV_ACCT for a DATEV account override on the item or OCRD.U_VPS_DTV_ACCT for the DATEV debtor account at the business partner. The name is limited to 18 characters and must follow the SAP namespace convention (max. 3 characters prefix, SAP-approved) to avoid collisions between add-ons. Over Custom Values (Formatted Search) field contents can be automatically determined by mathematical or logical formulas and database references. UDFs automatically appear in the service layer metadata model and can therefore be addressed by integrations via REST.
Demarcation
A UDF extends an existing object with additional fields – it does not create a new object. If a new standalone table is needed, a UDT to use (User Defined Table); if this table is to function like a genuine business object with its own interface, event control, and document behaviour, then a UDO (User Defined Object) necessary. UDFs are also not UDQ- Queries or Formatted Searches themselves — they are data containers that can be populated by Formatted Searches.
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