yea, it bugs me that the amended return payment part is not clear anywhere, Im not sure I trust to to actually happen. 

Ive been going on the tax agency websites and scheduling the payments for my clients that want it to come out on XX day....I print the client letter that shows its going to be direct debited (then change the box on the return), pay it online and I keep the confirmation page from the tax website for my records.

Couple extra steps for me, but great for client relations!