Offering bespoke codes for marketing purposes

>I can then login to my developer account at the end of the month and see that there are 50 sales using the code 'sarahsshop' and can pay Sarah accordingly.

Which is a great way to harvest and track user private info, so I see the point to your scheme.

However - you can't use the store to link specific users to a particular transaction, so...not going to happen.

You might look into the affiliate program. There you can generate any number of unique campaign identifiers, and purchases made via a link that includes that campaign ID can be tracked on the affiliate program web site. You could make an affiliate link QR code and if customers scan that code in-store and purchase the app it would be tracked for you. No manual entry of codes by the user (which is a non starter anyway, really - ain't nobody got time fo dat).

You can't provide a code that will give a discount on the purchase of the app itself though. Apple doesn't do that.

If you are talking about real-world goods sold through the app, then you could provide a discount code. It's just the app itself or IAPs therein that may not be unlocked using any mechanism besides StoreKit.

Thanks junkpile - that could assist me. I think KMT may have misunderstood me - I have no interest in the individual purchasers per se - rather I need to be able to know how many purchasing customers have been referred from a particular shop that that I can later pay a commission to the shop depending on how much business they have referred to me. I thought the discount may be a good way to encourage users to use the code as they probably aren't interested in helping out the shop owner.

With the suggestion of using unique identifiers I take it that I could use one specific link for each individual shop - perhaps print QR codes for the link onto a set of cards or have it on the counter/display in the shop so that I can establish by selecting the specific code how many people have purchased via 'Sarah's shop'?

I guess a further question in relation to the affiliate scheme is would I be able to generate such codes myself to provide the links to the shop owners, or would they have to sign up to something themselves? I would like to keep their part as simple as possible.

You can certainly allow a new user the option to fill out a simple questionaire telling you who told them about the app.

You can also allow the user to join that company's 'special users' club once they open your app. As a 'special user' they get....??... and you get informed that they joined. You could start a timer to see how long since they downloaded the app did they join the special users club for a particular store and only 'credit' the first store or the stores that they joined the first time they launched the app.