Most ERP buying mistakes are made before the demo. Retailers sit through two hours of slick screens, fall for the reporting dashboard and sign, then discover in month four that the system cannot allocate stock across channels the way the sales team promised it would. I have been called in on the selection side of more than twenty retail projects in the UK, and the same ten questions separate good purchases from expensive regrets.

If you are comparing retail ERP software in the UK, these are the questions vendors hope you will not ask.

Before the demo: how the vendor measures fit

The questions below should be asked before any vendor starts showing you screens. A vendor that cannot answer them in writing during the discovery phase will not start answering them after you sign.

1. Which retail verticals do you actually support in production?

Ask for reference sites in your sector and your size band, not logos from the homepage. A fashion retailer with 40,000 SKUs needs different allocation logic than a garden centre selling bulky seasonal stock. If the vendor's retail references are all one type, the demo is about to be misleading. Cross check the names they give you against the British Retail Consortium membership and industry event speaker lists to see whether the claimed deployments are credible.

2. How is the licence priced as you add channels and users?

Ask for the price of your expected configuration, not the starting price. Many retail ERP contracts charge per user type, per order, per channel connection or per warehouse. A price that looks reasonable for 20 users can double when you add a marketplace connector and a second fulfilment location. Ask for a written cost model for three scenarios: today, two years out, and if you double order volume.

Questions about your data

Data is where retail ERP projects quietly die. The system works. The data going in does not.

3. What does data migration actually cost and who does it?

The vendor will say migration is included. Ask what is included: extraction from your current systems, cleansing of product master data, mapping of stock and transaction history, or only the loading of standard templates. In my experience the retailer's team does the real work, and it always takes longer than planned. Read about the migration pitfalls in the five buying mistakes retailers make before you accept any migration estimate.

4. What integration effort is needed for each channel?

Your ERP will not replace your shop till, your marketplace connectors or your payment provider; it will sit behind them. Ask for the integration architecture diagram and the expected effort per channel. If the vendor says "native connectors for everything", ask who maintains each connector and what happens when Amazon or Shopify changes their API. The market insights published by IMRG regularly show how quickly the channel landscape shifts in UK online retail, which is a fair measure of how often your integrations will need maintenance.

Questions about stock and orders

This is the part of the demo where most retailers stop listening and start dreaming. Keep your notebook out.

5. How does the system allocate stock across channels?

Ask for a live walkthrough of a real allocation rule: priority by channel, reservations by basket, safety stock per channel, and what happens at the exact moment two channels sell the last unit. The answer tells you whether overselling is a design problem or a configuration problem in the platform. If you already sell across shop, web and marketplaces, this single answer is worth the licence fee on its own.

6. Can it orchestrate an order across multiple fulfilment locations?

Ask what happens when a customer orders three items and they are split across two warehouses and a store. Does the system create one order with multiple shipments, allocate the stock, generate the labels and update the customer automatically? Or does a coordinator do it by hand? Split fulfilment is where single platform promises break, so this is a natural point to compare with best of breed versus single platform architecture.

7. How are returns represented in stock and in margin?

Returns are not a logistics event, they are a financial one. Ask how the system values returned stock, whether it restores sellable stock to the correct channel, how it handles refunds against the original payment, and whether return reasons flow into reporting. The returns research shared by Retail Economics shows how much of retail margin is tied up in return handling, which makes this question more important than most buying teams realise.

Questions about the contract

Everything up to this point was about the product. The next two questions are about the relationship after signature.

8. What are the upgrade and support obligations?

Ask how often the platform releases updates, whether customisations block upgrades, and who pays for regression testing. A heavily customised ERP can become a system you cannot upgrade, which is a slow moving budget problem. Ask for the average upgrade cost their UK customers pay, not the brochure answer.

9. What does leaving look like?

Ask for the data export terms and the contract exit clauses in writing. Retailers rarely plan for the day they replace the ERP they are buying today, but the ones that negotiated clean data access avoided a second migration disaster later. If the vendor refuses to commit to export formats, that is a signal about how they treat customers generally.

Questions about delivery

10. Who implements it, and what happens when the timeline slips?

Ask whether implementation is done by the vendor's team, a partner or the retailer's own staff, and what the fixed price actually covers. Compare the answer with realistic durations for implementation timelines and probe how slippage is priced. Also ask for the named project manager's track record, not the account manager's.

Using the answers

Score every vendor against the same ten questions in a written matrix before any negotiation. The scoring is less important than the discipline of forcing comparable answers. If you are earlier in the journey, start with the signs that you are ready for an omnichannel ERP and the build versus buy analysis, because both change which questions matter most.

One final observation from client work: the best vendors answer the hard questions slowly and honestly. The worst answer them quickly and smoothly. A long pause followed by "we would need to check that with the product team" is not a red flag. It is the sound of a vendor that has not lied to you yet.