You can't directly filter price list items by whether they have a fee — poplatky is a relation, not a property, so trying to filter by it will result in a Vlastnost 'poplatky' neexistuje error. However, there are two workarounds available.
Via the price list and the fee relation
GET /c/{firma}/cenik.json?limit=0&relations=poplatky
You get all price list items, and those with a fee will have the poplatky relation populated — items without a fee then need to be filtered out by the caller. In the test data, 21 out of 290 items had a fee.
Via the fee register
The opposite approach is more efficient: you query the fees directly, and use the cenikOtec field to find out which item they belong to.
GET /c/{firma}/poplatek/(cenik='code:RECYKLACE 5').xml?detail=custom:cenikOtec(kod,nazev)&includes=/poplatek/cenikOtec
Register fields poplatek:
Field | Meaning |
| The price list item that represents the fee (has the Fee stock type). |
| The price list item to which the fee is assigned. |
| The quantity and type of the fee. |
💡 If you'd like to get the parent item's properties directly instead of links, expand the relation using the includes parameter — this principle is described in the article Using includes.