Define the outcome first
A QR scan establishes that a link was opened. It does not establish that a new customer was created. Choose an outcome the business can record, such as a paid order or a qualified appointment. Give page visits, enquiries and sales separate event names and counts. Keep a campaign register with the audience, offer, mailing date, creative version and total cost.
Identify each response route
Use tagged links behind QR codes and a readable campaign URL. Google’s campaign parameter documentation explains source, medium and campaign values. Keep those values consistent between versions. Telephone responses need a separate recording process. Some customers will search for the brand later, so tagged links will capture only part of the influence.
Calculate contribution after costs
Subtract product, fulfilment and discount costs from matched sales before comparing the result with marketing spend. For a hypothetical campaign costing $600, $1,200 of sales is insufficient to establish profitability. If those orders contribute $420 before marketing, the immediate result is $180 below campaign cost. Include design, print, postage and list preparation in the calculation.
Compare with customers who received no card
Where feasible, randomly reserve a comparable group from the mailing. Compare purchase rates and contribution over the same period. Small samples and overlapping campaigns can make the estimate uncertain. Use our planning guide to set the rules before launch. The USPS customized mail guide describes additional response options. For customers moving through AI answers and search, see cross-AI attribution. Report observed responses separately from estimated influence.
Frequently asked questions
Does a unique QR code prove who scanned?
A code identifies the piece or link. Forwarding, shared devices and repeated visits mean it does not reliably establish the identity of the person scanning.