Designing and building a KSeF invoicing app that 3,000+ people use

01

About InvoiceRate

We handled the research, UX, UI, frontend, backend, hosting and store submission.

What it is: A mobile workspace for invoices, KSeF, tax and payments. The bottom navigation has Home, Invoices, New, Clients, and More, so revenue, balances, KSeF, reports, and settings are a tap away on a phone.

Where it runs: Live on the App Store and Google Play, with a companion site at invoicerate.com. It was built for the Polish market first, with PLN, VAT, PIT, ZUS, JPK, UPO evidence, bilingual invoices and official KSeF workflows. The everyday interface is written for people who aren't accountants.

Reach: 3,000+ downloads, 3,000+ users and 10,000+ daily visits.

02

The problem

Freelancers and small teams often handle billing between jobs, on site or after hours. A lot of accounting tools are built around dense desktop dashboards and long forms, and they assume tax knowledge the owner may not have. So invoices go out late, payments get forgotten, and the KSeF evidence ends up stored somewhere else. It also makes a basic question hard to answer: “What is still missing before this month can go to the accountant?”

A small business owner usually isn't looking for an accounting platform. They want to issue a clean invoice, know if KSeF accepted it, mark it paid when the money arrives, sort out what needs review, and send complete monthly records to the accountant without chasing rows in a spreadsheet.

03

What we designed and built

Home: A monthly view of total revenue, receivables, VAT to pay, overdue amounts, KSeF status, quick actions and recent invoices.

Invoices: Customer balances with a 30-day selector, totals for pending, overdue, and collected invoices, and actions for sales invoices, supplier invoices, and KSeF imports.

Payments and analytics: Record payments as they arrive and see monthly totals update across revenue, receivables, VAT, PIT, ZUS and reporting records. You can see where the month stands without the screen turning into a copy of an accountant’s desktop software.

Clients: Save a client once and reuse the details on future invoices.

More: This tab groups Analytics and tax, KSeF Centre, monthly reports and registers, accounting and settlements, recurring invoices, and business profile.

Reports: Each month’s records pull together sales, purchases, VAT, PIT, ZUS, JPK, payment status, and anything still waiting for review. You can then export them for the accountant.

KSeF Centre: One screen for the connection status, checks, accepted, queued and rejected documents, configuration, and invoice evidence.

04

Design decisions

Light and legible: The interface is white with one green accent and muted status colours, so the visual weight goes to money, evidence, and unfinished actions.

Faster invoice creation: The form follows the order people usually think in (who, what, how much, and when), and saved defaults mean you don’t type the same details twice.

Visible evidence: KSeF connection, exchange status, accepted, queued and rejected counts, UPO-style evidence, payment status, and reporting readiness stay on screen, so people can see what’s done and what still needs review.

Local-first storage: Books and documents stay on the device, with encrypted backup. The app only goes online when KSeF or another online action the user chose needs it.

05

Outcome

InvoiceRate is live on iOS and Android. We designed, built and released the product, including invoice creation, KSeF handling, payment follow-up, tax preparation, and accountant handoff.