For decades, the high street has remained a refuge for digital refuseniks. Sure, you’re now able to 1-click a multipack of quilted two-ply from the comfort of your loo seat using an Andrex Amazon Dash button. But, offline, in an actual shop, you hand over the money and you’re done. Receipt in the bag? Yes, please.

No more. As if the threat to paper were not grave enough, the old-fashioned till receipt is in trouble. How much you care probably informs your response to the increasingly familiar checkout refrain: “Can we email you your receipt?”

Shops including Gap, Topshop and Mothercare now routinely offer e-receipts. Apple stores have been doing it for ages. The benefits are plain: an email can’t end up in the wash. Better for online tax returns and trees. But to what extent are retailers motivated by more than marginal convenience – and what else is in store?

That e-receipts are important to retailers became clear to a friend who politely requested a paper one – rather than hand over his email address – last month. He had gone to buy an emergency T-shirt at Nike after a coffee spillage. The shop assistant seemed surprised and disappointed, and had to go to a different till. Seconds were wasted, but my friend, who paid cash, appreciated his anonymity.

A Mothercare e-receipt shows why stores don’t like anonymity. It comes as an attachment, but the email includes an online survey request, a plug for a Dutch buggy brand and, right at the top, an invitation to download the Mothercare app.

E-receipts are the low-tech tracer round in a coming barrage. The response of the high street to the threat of online-only stores is to deploy the same ammunition. Shops, which have always been glorified warehouses, are blurring the lines between online and offline consumption in an attempt to get to know us so that they can sell us more wherever we are.

Mothercare’s app is part of this bricks-and-data approach. You can shop on it but it also encourages store visits, with a finder function and a way to pull up reviews of the really expensive car seat in front of you. Scan receipts straight from your phone to return an item. A lullaby player brings the brand into your life as well as your bank statement. It’s not just an app, it’s a “companion”.

“Retailers are trying to move to a long-term relationship with customers because loyalty as we once thought of it is pretty much dead,” says Colin Strong, head of behavioural science at market research group Ipsos and author of Humanizing Big Data. The internet has helped consumers take power away from retailers. We compare prices and try stuff on in store before ordering it online for less.

“Servitisation” is one way brands win back loyalty. “I call it the Nespresso effect,” Strong explains. “It’s buying into an ecosystem and not having to make decisions while the brand learns more about you.” In a clothes shop, that means using your data to personalise shopping. “They want to bring the functionality and experience that people have online into the store,” says Dan Hartveld, who helped build Ocado’s shopping systems. He is now head of tech at Red Ant, whose clients include Halfords and Topshop.

Emails mean stores can gather your online and offline shopping history. “This single-customer view has been the holy grail for about five years but now we’re going further,” adds Hartveld. Red Ant provides Topshop with iPads so that assistants can pull up a customer profile right on the floor, and check you out. For now, the assistant still needs an email address, but Red Ant is working with a luxury retailer on a more sophisticated system (he can’t say who); customers who have the store’s app on a phone in their pocket will be sensed as soon as they walk in the door. Assistants will be able to greet them and present the shoes, say, that they were looking at online before they left the house.

US retailers are a step ahead. Department store Nordstrom’s “innovations lab” can track the movements of consenting customers within the store. The marketing team finds trending products on Pinterest and updates in-store promotions. At clothing brand Rebecca Minkoff, shoppers can go all Minority Report on giant mirrored touchscreens, calling up items to be sent to a changing room, throwing in a drink order for good measure.

Cute, but what does this all mean for my coffee-stained friend and his small-data instincts? “The problem is that shop assistants aren’t yet explaining what the nature of the email request is,” says Renate Samson, chief executive of data guardian Big Brother Watch and member of the government’s privacy and consumer advisory group. “‘Will you be retaining my address for marketing, or sharing it with third parties?’ It must be clearer.”

Nike did not respond to questions about its e-receipt policy. Topshop said it introduced them last year and that there is no obligation. Customers must opt in to receive marketing emails, a statement goes on. New EU data laws due to come into force in 2018 will, Brexit permitting, demand a more direct opt-in approach (no more “untick this box if you don’t want to receive a million emails”) and clearer information. But resistance is futile; the privacy-aware will need become ever more vigilant if they want to stay under cover.