How long does vendor have to take money from account?

I made a purchase from an online site a couple of months ago and received said purchase. I looked over my statements recently and noticed the money wasn't taken from my account. What is the maximum time they are allowed, to take a payment from my account? Can this payment leave my account in a years time?

Why don't you just notify them of their error and they will take the money out of the account immediately?

I will when the banks reopen. It just got me curious as to how long they can defer taking a payment. Had it been for a large amount and I hadnt noticed and the payment was taken out months later when I mightn't have sufficiently funds in the account to cover the payment it could result in unwanted penalties in the account. I was asking a fact based question, not for moral advice.