@irurzo if you add "&xml=t" to the end of the URL of that Vendor Prepayment, you can look for <machine name= in the xml and that may show you the correct id. i.e. on Sales Orders <machine name="item" would indicate the "item" sublist

or maybe use a plugin: https://chrome.google.com/webstore/detail/netsuite-record-json-view/ibkdphopcbimokejnhhgelcancfabhba

I already tried that, the name of the list if I do the XML=T is bill which didnt work either when using

getLineCount('bill)