For smaller companies, I also don’t agree with showing real stock values. An Amazon can ‘afford’ to be honest as their stock is often in the dozens, if not hundreds on popular items. Sure, low stock numbers create a sense of scarcity which may aid conversions but having true, low stock numbers on all your products gives away a lot to competition IMO. So with all these things, as always, it depends. There’s no definite right or wrong and everybody should, like with everything websites, test to see what works best. A/B or multivariate, it just gives you real answers rather than speculation you’ve read on a blog or forum written by someone you don’t know and who’s business case you don’t understand. I’ve yet to see two serious e-commerce businesses which work in the exact same way.

Anyway, if you’re planning on visiting London anytime soon, give me a shout and as a fellow coder/Mage-merchant I’ll be happy to take you wakeboarding. (Just checked out the pics.) Here in SW London we’re quite spoilt for choice in terms of lakes and cables, including the new System 2.0 straight cables which I checked out last weekend (arms still ache).

I think you’re right about the timing being important. If you deduct stock when you get an order, but before taking payment, it can become a denial of service vulnerability, because someone could place unpaid orders on products to ‘out of stock’ them. If you deduct stock when you get payment, then with nearly instant payment providers like Google Checkout, you open up a race condition where sometime between the order being placed and the payment clearing (normally 15 minutes) someone else using an instant payment service like Paypal could snap up the last item.

This becomes more complex again if you have multiple sales channels drawing on the same stock as the timing problems above plus the stock level update frequency come in to play.

Our solution isn’t perfect, and I’m not sure there is a perfect way to do it (some OPRE expert lurking might care to weigh in on that?). The best I think you can do is find a frequency of updates and a policy on ‘out-of-stock’ness that keeps sales flowing while at the same time avoids frustrating the customers who do pay you for something, then do not get it.

That said, made-to-order products, where there is a history of complication in the production, are never ‘in stock’ as far as I’m concerned!

Another level up is do you subtract stock when someone has paid for it, or when it left your warehouse? A paid-for item can come back in general stock for many reasons. Fraud, they don’t want it delivered yet, cancellations. It’s not always black and white. And inevitably, the one punter where it goes wrong will go an moan on a blog 🙂 whereas with the other 99 orders, everything turned out fine and everybody was happy.

So IMO, it all depends on your exact business model, what you sell, the expectations in terms of delivery speed, the type of customers etc. It’s a trade-off between not disappointing customers in those cases where your slight overpromise goes wrong vs not wanting to loose out on orders by showing real stock, when 24 hours later it could have been back in stock.

Having said all that, I do agree with your views. But I have yet to see a Magento module which is flexible enough for our use-case to show more-accurate-than-just-“in stock” yet not fully “out-of-stock” either. I’m looking for something in between, have seen a few attempts but have yet to find the holy grail.