Hello Voangaushooss88
We are not the SBB Customer Service, therefore our reply is not official.
From experience, we know that in case the payment is not made in time, the invoce will enter the dunning phase.
The unpaid Halbtax remains valid over a very short period of time until it is blocked, just to accept eventual late payments that were made around the due date.
Unpaid abonnements may lead you to a fine, a surcharge of at least CHF 70 upon ticket check, while still using it.
We suggest setting up eBill, by doing so you will not forget the payment in the future.
Kind regards,
Roland