The deadline for collecting an order you chose to pick up. Your order shows it as Collect by and a date and time.
It starts when the store marks the order ready, not when you paid. So the clock does not run while the store is still packing.
How the date is worked out
The store's collection window — a number of hours — added to the moment it was marked ready.
Plus a whole day for every day in between that the store or the pickup point is closed.
That second part is the one nobody expects, and it is in your favour. If an order is ready on a Saturday evening and the point is shut on Sunday, Sunday does not count against you. The same for a holiday the store has marked closed.
So the deadline you see is already adjusted. You do not need to work out which days to add — the date on the screen is the real one.
What happens if you miss it
Depends on the store's terms, snapshotted onto your order at checkout so they cannot change under you:
Usually a fee. A no-show charge on the order, as a percentage.
Sometimes the item goes back on sale, if it is perishable or the store marked it as spoiling.
Either way you are told before the deadline, not after it. What happens if I do not collect?
If you cannot make it
Message the store. Before the deadline, not after. A store that knows you are coming on Thursday will almost always wait; a store hearing from you on Friday about Tuesday will not.
This is the whole of the advice and it works nearly every time. The fee exists for people who simply never came.
Where to find it
On the order. It also appears on the store's side, so both of you are looking at the same date — there is no version of this where you each believe a different deadline.
If the store has not marked the order ready yet, you will see that instead: the store will tell you when it is ready.
For sellers
The window is yours to set, and the thing to get right is the pickup point's own open days, because they feed the calculation. A point marked open seven days a week when it is really shut on Sundays gives buyers a deadline that is a day short. How to offer pickup
More: how pickup works, what is a pickup point, where is the pickup point.