Buying Train Tickets

You can check in and out at the gate with your debit or credit card. You pay full fare. Look www.ovpay.nl/en. With this method you can travel on any train. You may need to purchase additional supplements separately.

In the NS app you can buy train tickets in advance with a discount of up to 60 percent. These train tickets are time-bound, not valid during rush hour. Purchased train tickets are not exchangeable and no money back. Purchased is purchased.

The earlier you book, the cheaper the train ticket. You have to open the gates with the received QR code.

Or look www.ns.nl/spoordeelwinkel

Intercity direct and EuroCity between Schiphol and Rotterdam must be purchased supplement. If you want to travel to Rotterdam without supplement, you can travel via Leiden or via Woerden. Supplements can be purchased at the machine, NS app and the red pole on the platform.

All domestic travel is organised as commuter services. You just need to have a valid ticket, no reservations exist.

The easiest way is to use your bankcard (debit or credit). For each trip you just check in (at departure) and out (at arrival) and the fare will be charged to your account one or two days later. 

Buying tickets in advance as @Seinhuis suggests is given the short distances (no or minimal reduction) you travel not advisible in my opinion, especially because you have to order them far in advance and they are inflexibel because they are timebound and cannot be changed or cancelled after purchase.

Be aware that trains and buses in the Netherlands are more expensive than in most other European countries.

Regarding using bank card to pay, how about children?

How old are the children?

My children are 9 and 12yo.

We are travelling from 1) Amsterdam Sloterdijk to Rotterdam Blaak and back to Amsterdam on a Saturday and 2) from Amsterdam Sloterdijk to Zaanse Schans and back to Amsterdam on a Sunday. What are the best options for us? Group ticket or individual adult/child ticket?

Thanks in advance!