Payment Solutions

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Payment Solutions – we enable transactions

Online payments look simple to the customer. Behind the “Pay now” button sits a chain of moving parts: gateways, banks, fraud checks, tax rules, refunds, settlement, reconciliation, and customer support. When any one of those parts is brittle, you feel it quickly in lost sales, manual work, and awkward disputes.

At Gislen Software, we build and integrate payment solutions that are reliable in day-to-day operation, easy to extend, and straightforward to support. We work with both product companies and established organisations that need payment to “just work” across web, mobile, and back-office systems.

We have implemented and maintained payment solutions for:

  • a restaurant app-payment start-up
  • a peer-to-peer lending fintech business supporting multiple currencies
  • a membership, conference and training platform for one of Europe’s largest medical associations

We also support other clients where payment is only one part of a larger solution, but a part that has to be treated with care.

Build

  • We design and implement payment flows that fit your business, not the other way round.
  • That includes checkout and in-app payments, subscriptions, invoicing, refunds, and the less glamorous parts such as reconciliation files, admin tools, and audit trails.
  • We build on your current stack or modernise in steps, so you can improve payment without freezing the rest of your roadmap.

Integrate

  • Payment rarely lives in isolation.
  • We integrate gateways and wallets with your e-commerce platform, ERP/finance system, CRM, subscription engine, order management, identity provider, and support tools.
  • We also handle webhooks and event-driven updates, so stock, fulfilment, and customer communication stay in sync even when payments are delayed, part-paid, or reversed.

Run and improve

  • Payments are an operational system.
  • We help you monitor failures, spot unusual patterns, handle chargebacks, and reduce manual work in finance and customer service.
  • When regulations or gateway APIs change, we keep your solution compliant and stable.
  • If you need ongoing support, we can provide maintenance and a predictable way of making improvements over time.

Gateways and payment methods

Clients come to us with different constraints: existing contracts, preferred acquirers, target markets, or a platform they are locked into. We work with common gateways and providers such as PayPal, Stripe, Klarna, Braintree, and many more, and we can integrate with region-specific methods such as Swish where required.

If you are choosing a provider, we can help you compare options based on what matters in practice: supported methods, settlement speed, reporting, dispute handling, API quality, pricing model, and how well it works with your existing systems.

What we typically build

Online checkout and in-app payments
Card payments, pay-by-link, QR payments, saved cards, one-click checkout, and region-specific methods where relevant.

Subscriptions and recurring billing
Free trials, upgrades, downgrades, pro-rating, dunning flows, and customer self-service for payment details.

Marketplaces and split payments
Where you need to route funds to multiple parties, manage fees, and support payouts.

Invoicing, EDI and “track and trace”
Electronic invoices, EDI messaging, payment status updates, and integration with logistics or service delivery milestones.

Back-office tooling
Admin screens for refunds and adjustments, dispute handling, customer support views, and finance exports that reduce spreadsheet work.

Getting the details right

A payment solution succeeds or fails in the edge cases. We pay attention to the parts that usually cause trouble later:

  • Security and customer trust: tokenisation, sensible data handling, least-privilege access, and clear audit logs
  • Authentication and regulations: support for modern verification flows where applicable, without adding friction for customers
  • Fraud and disputes: chargeback workflows, evidence capture, and basic fraud controls that do not punish legitimate customers
  • Operational robustness: idempotency, retries, safe handling of duplicate callbacks, and clear error reporting
  • Finance and reconciliation: settlement reports, fee breakdowns, refunds, partial captures, and clean exports into your finance processes
  • Tax compliance across markets: experience with complex international tax handling, including US sales tax rules across different states and EU/EEA VAT compliance for cross-border e-commerce.
  • Multi-currency and international use: currency conversion rules, rounding, VAT/GST considerations, and local payment preferences

We explain these topics in plain language, so business owners, finance, and customer service can understand how the system behaves.

Digital payment solutions in action

Business Analysis

Software Development

User Experience

Legacy Migration

Mobile Developmentx§

How we work

  1. Short discovery to map your payment flows, failure points, and operational needs
  2. Design and integration plan that covers customer experience and back-office reality
  3. Implementation and testing using sandbox environments, realistic scenarios, and clear acceptance criteria
  4. Go-live support with monitoring, dashboards, and a practical runbook
  5. Ongoing improvement based on real payment data and support feedback
What do you mean by “payment solutions”?

We mean the full chain around taking money digitally: checkout or in-app payments, gateway integration, refunds, subscriptions, settlement, reconciliation, reporting, and the back-office workflows that keep finance and customer service running smoothly.

Do you only integrate gateways, or do you build complete payment flows?

We do both. Some clients need a clean integration to a gateway. Others need end-to-end payment flows, including order handling, invoices, refunds, admin tools, audit trails, and reporting that makes reconciliation practical.

Which payment providers can you work with?

We work with common providers such as PayPal, Stripe, Klarna, Braintree, Payson and similar services. Where required, we also integrate region-specific methods such as Swish, and point-of-sale solutions such as Zettle (iZettle) for hybrid retail flows.

How do you help us choose the right payment provider?

We compare options based on what tends to matter in real operation: supported payment methods, settlement speed, reporting and reconciliation quality, dispute handling, API reliability, pricing model, and how well the provider fits your existing systems and markets.

Can you support multiple payment methods in one checkout?

Yes. We can implement checkouts that support cards, wallets, pay-by-link, QR payments, saved payment details, and region-specific methods, with clean fallbacks and clear customer messaging when something fails.

Can you build subscriptions and recurring billing?

Yes. We build subscription flows including free trials, upgrades and downgrades, pro-rating, failed-payment handling (dunning), and customer self-service for updating payment details and viewing invoices.

Do you handle marketplaces and split payments?

Yes. Where a platform needs to route funds to multiple parties, we can implement split payments, fee handling, and payout flows, including reporting that helps both your finance team and your sellers.

How do you make payment integrations reliable?

We design for the awkward cases: retries, duplicate callbacks, partial payments, delayed confirmations, and safe handling of timeouts. We also include monitoring and diagnostics so issues are visible quickly and can be resolved without guesswork.

How do you deal with refunds, chargebacks, and disputes?

We implement clear refund workflows, capture the data needed for dispute evidence, and support chargeback handling processes. We also help reduce support load by making payment status and outcomes easy to understand for both customers and staff.

What about security and compliance?

We follow good practices such as token-based handling of payment details, least-privilege access, secure data storage, and audit logs. Where relevant, we also support modern verification flows and ensure the solution stays aligned with provider and regulatory requirements.

Can you help with tax and multi-currency payments?

Yes. We have experience with multi-currency handling, rounding rules, and local preferences. We can also support cross-border tax requirements such as EU/EEA VAT handling and US sales tax rules across states, depending on how your business is set up.

What does a typical payment project look like with you?

We usually start with a short discovery to map payment flows and failure points, then create a design and integration plan. After that we implement and test in sandbox environments with realistic scenarios, support go-live with monitoring and a runbook, and then improve based on real payment data.

When to talk to us

You will likely benefit from our support if you recognise any of the following:

  • You are expanding to new markets and need more payment methods or currencies
  • Your finance team spends too much time matching transactions to orders and invoices
  • Chargebacks, failed payments, or unclear refunds are creating customer support load
  • You need to replace a gateway, reduce vendor lock-in, or modernise an older integration
  • Payment is holding back product improvements because the current setup is fragile<

If you want to discuss a new build, a migration, or simply a review of what you already have, we are happy to talk through options and trade-offs.

Contact us to discuss how we can help you