Carbon Zero

Buy now, pay later at 0% interest, from purchase to payment in under a minute.

Lead Product Designer
Design sprint lead
Research to handoff

Jump to key decisions

Carbon Zero new purchase screen with a payment plan split into instalments

The problem: Carbon Zero lets people buy today and pay in instalments at 0% interest, but the flow was slow, asked for too much, and didn’t make the ‘zero’ obvious.
What I did: I ran discovery with customers, merchants and stakeholders, led a design sprint, and redesigned the dashboard, purchase, payment and repayment flows.
The result: A faster purchase flow with an on-the-spot payment option, a prominent ‘pay early’ action that improved early repayments, and shareable receipts merchants trust.

interest, communicated at every step: 0%
target from purchase to payment: < 1 min
instalments to split a purchase: 4
long-term goal: consumers’ choice to pay: Top 3

Company: Carbon MFB
Role: Lead Product Designer
Team: 3 designers, 1 PM, 5 engineers, 1 scrum master
Platform: iOS and Android
Tools: Figma, Miro, Confluence, Jira

Problem & context

Credit only works if people trust it, and understand it in seconds.

Carbon Zero is a Buy Now Pay Later product: customers buy today and split payments over time at zero interest. The long-term goal was for it to become one of consumers’ top three ways to pay.

To get there, the whole flow had to feel instant and the ‘0% interest’ promise had to be unmistakable, while still protecting the business from missed repayments.

Constraints

Repayment protects the business: it had to stay prominent without feeling threatening
Card requests could take up to a week, too slow for an in-store purchase
Under NDA: personal details in the screens below are blurred

Role & team

I led design and facilitated the sprint that shaped the product.

That’s me
Chukwuemeka Iheonye
Lead Product Designer
Discovery, sprint facilitation, interaction design, UI and prototypes; led two designers.
Design
2 Product Designers
UI production and design QA.
Product & engineering
PM, 5 engineers, scrum master
Scope, build and delivery.

Process

A design sprint took us from risks to sketches to a plan.

01
Listen
Conversations with customers, merchants and stakeholders to understand what was slowing purchases down.
02
Map
A sprint map of the long-term goal, metrics to watch, risks, and ‘How might we’ questions.
03
Sketch and decide
Crazy 8s where no idea was too wild, then voting on the concepts to prototype.

Sprint map with long-term goal, metrics and risks — Mapping goals, metrics and risks.

Crazy 8 sketches pinned to a decision board — Crazy 8 sketches, then a decision.

Key decisions

Each decision made buying faster or repaying easier.

Decision 01
Pay by transfer, on the spot
Getting a Carbon card could take up to a week, too slow for someone standing at a till.
What we chose
Added merchant account transfer as a payment option alongside the card.
Why
Customers can complete a purchase immediately, which is what ‘buy now’ should mean.
Decision 02
Choose the amount and the split together
The old purchase flow asked for details across several screens before showing a plan.
What we chose
One screen to enter the amount, see the instalment plan, and adjust the down payment.
Why
Fewer steps, and the 0% interest is visible right next to the numbers.
Decision 03
Make ‘pay early’ impossible to miss
Unpaid credit hurts the business, and early repayment was hidden.
What we chose
A prominent ‘Pay early’ button on purchase details, with the full repayment schedule below.
Why
It improved early repayments without making customers feel chased.
Decision 04
A receipt merchants can trust
There was no way to prove a payment had gone through.
What we chose
A shareable transaction receipt for every purchase.
Why
Customers can show proof of payment instantly, which builds trust on both sides of the counter.