On Feb 21, 8:49*am, JS wrote:
On 19 Feb, 20:59, Jamie *Thompson wrote:

On Feb 19, 5:56*pm, JS wrote:

System has no way of knowing whether journey was started within zones
of Travelcard or beyond, hence the charge.

The point I was making is that *wherever* you started your journey,
the "maximuum" fare you could possibly pay is that of the zones not
covered by your Travelcard, and IMHO that should be the penalty. I.e.
Given a z12 Travelcard, if you actually started your journey at
Canon's Park, but didn't touch in, being charged as having come from
Willesden Green would be the penalty. The principle should always be
that there should be no requirement to touch in within the zones where
your Travelcard is valid.

So, I have a Z3-4 on my Oyster card.
I make a journey without touching in but touch out at a Z4 station.
What should I be charged for?
A Z1-2?
A Z5-G?
TfL fare scale?
NR fare scale?
Through fare scale?
Hence the max fare charge

Ah, what I managed to edit out of my example was the
destination...which was supposed to be Stanmore.

However, in your example, if you didn't touch in, but touched out in
z4 with a z4 Travelcard you're not charged anything, which isn't the
point I was making. I was referring to extending your journey out of
your zones without touching in. In that specific scenario, I think
charging from the validity of your zones is quite reasonable, as any
loss should be minimal.