H345 is the 5% off code:

This offer valid for five (5) percent off the best available regular (full) adult, senior, disabled adult, Student Advantage and Veterans Advantage, AAA and NARP members discounted adult rail fare. Disabled passengers must call 1-800-USA-RAIL to make reservations using this special offer and to receive the Amtrak discount for disabled passengers. Offer valid for reservations: 08Sep03 - 13Dec03 and for travel 08Sep03 - 30Apr04. Blackouts apply for the following dates: 25Nov-02Dec03, 19Dec03-04Jan04, 13-16Feb04, 08-12Apr04. Up to 2 children ages 2-15 may accompany each paid adult at 1/2 of the discounted adult rail fare. Not valid on Acela Express®, Metroliner®, Canadian portions of joint Amtrak/VIA Rail service to Ontario, 7000-8999 Thruways or for local travel on Northeast Corridor trains (Washington, DC, to Boston, MA) departing at peak travel periods. Fares, routes and schedules subject to change without notice. Other restrictions may apply.