NJ Transit sends a receipt by email when you buy tickets on its website: it goes to the address you entered during the purchase. That email is the receipt to keep. You do not need an account to buy, but an account is what you log in with to generate your ticket barcodes later.
The emailed receipt
Every web ticket purchase triggers a receipt email to the checkout address. If you buy tickets for someone else, use your own email at checkout if you are the one claiming the cost; the receipt follows the address, not the traveller.
Account or guest purchase
NJ Transit says an account is not required to buy tickets. With one, you log in to generate the ticket barcodes. Without one, the email is your only copy of the purchase. Move it out of the inbox to a folder you keep for travel costs.
Refunds on web tickets
One-way and round-trip tickets bought on the web are not refundable, according to NJ Transit's web ticketing FAQ. A trip you did not take still leaves you with a receipt for a paid ticket, which is worth noting on an expense claim if your employer reimburses unused fares.
Other questions
The web ticketing FAQ covers downloading and printing tickets, not reprinting receipts. For a receipt that never arrived, contact NJ Transit Customer Service through njtransit.com.
NJ Transit receipts saved from your inbox
Rail and bus tickets into Newark or Manhattan are a regular line on many New Jersey expense reports. Email receipt capture finds each NJ Transit receipt email and files it with the fare and date. Paper tickets or a printed receipt can go in through the receipt scanner, and the trips line up on your expense report.