# Update field

`PATCH /v1/userfields/tasks/:id`

Bitrix24 method: `task.item.userfield.update`. Scope: `task`.

Only `label`, `mandatory`, `sort`, `settings`, `items` are accepted. `fieldName`, `userTypeId`, `multiple` return `400 IMMUTABLE_FIELD`; unknown properties and an empty object return `400 INVALID_PARAMS`. label is a string or language map, mandatory is boolean, sort is an integer.

An item with `id` must include a nonempty `value`; to delete it, send `del:true`. Otherwise Bitrix24 would silently delete the variant. Unmentioned variants stay. When xmlId is omitted, the wrapper preserves its current value; a new item without id is added. Example: `{"items":[{"id":8,"value":"New name"},{"id":9,"del":true}]}`.

The field is read before writing; system fields return `403 SYSTEM_FIELD_PROTECTED`. Response contains the field read back after writing. Bitrix24 may normalize settings and labels of uninstalled languages on any update.

## Errors and access

Missing scope: `403 SCOPE_DENIED`. Portal plan without TASK_CUSTOM_FIELDS: `403 TASK_CUSTOM_FIELDS_UNAVAILABLE`, including reads. Nonexistent fields: `404 ENTITY_NOT_FOUND`. Invalid input: `400`; Bitrix24 business refusals: `422`. Bitrix24 write permission refusals: `403`. Reads accept READONLY keys; writes require READWRITE and portal administrator rights. Writes are never retried automatically. After a timeout, the outcome is unknown: reread the field before another write.

[All task field operations](/docs/userfields/tasks)

List item `items.sort` must be positive: Bitrix24 ignores zero. To clear a single-list default, select another item with `def:true` in the same PATCH; otherwise the response is `400 INVALID_PARAMS`. If reading fails after a confirmed write, `502 TASK_USERFIELD_READBACK_FAILED` includes `error.fieldId` and `error.writeConfirmed:true`: repeat GET, not the write.