Question: With a Day ticket for Germany (Quer-durch-Land-Ticket) one can travel with all local trains in Germany. 

Is this ticket also valid on the train to/from Venlo in The Netherlands or is a separate ticket from Kaldenkirchen required for crossing the border?

Answer: 
No, the Quer-durchs-Land-Ticket [is valid at a few short sections close to the border in Austria and Switzerland](https://www.bahn.de/p/view/mdb/bahnintern/angebotsberatung/regio/laender-tickets/pdfs/2017/mdb_242073_ab_dez_2016_geltungsbereich_quer-durchs-land.pdf), but not in the Netherlands. If you are travelling on a Saturday or Sunday, you may be able to use the Schönes-Wochenende-Ticket, [which *is* valid between the border and Venlo](https://www.bahn.de/p/view/mdb/bahnintern/angebotsberatung/regio/laender-tickets/pdfs/2017/mdb_242748_0117_geltungsbereich_schoenes-wochenende-ticket.pdf).

With the Quer-durchs-Land-Ticket, you must probably in addition buy a VRR ticket from Kaldenkirchen to Venlo for €2.70. In theory, it should be possible to issue an international full-fare ticket from Venlo(Gr) (this is the border tariff point) to Venlo for currently €2.40. If you go to a staffed DB ticket counter, they may be able to sell such a ticket.
Unfortunately you need a separate ticket for the trip to/from Venlo. There is a [pdf-document](https://www.bahn.de/p/view/mdb/bahnintern/angebotsberatung/regio/regionale_tickets/2018/mdb_269392_qdl_april_2018_geltber.pdf) (only in German) that lists all trains that you can use with the Day ticket for Germany (Quer-durch-Land-Ticket) - there are some train lines in Austria, Switzerland and Poland, but none in the Netherlands.

Another option could be to use the Weekend ticket for Germany (Schönes-Wochenende-Ticket) which includes the train line Kaldenkirchen – Venlo adn also the bus line 929 Niederdorf – Venlo. Here is the [source](https://www.bahn.de/p/view/mdb/bahnintern/angebotsberatung/regio/regionale_tickets/2018/mdb_269394_swt_april_2018_geltber.pdf) (also only in German)