BillingEngine vs Sept Fifteen: Which Is Better in 2026?

BillingEngine is an invoicing and light bookkeeping application for freelancers, tradespeople and small businesses in Germany. It was built around one idea: sending a correct invoice should take a few clicks, and the data behind it should be useful afterwards.
Every invoice you create is an e-invoice under the European standard EN 16931, so you meet the German e-invoicing requirements without extra tools or conversion steps. You can create and send invoices and track their status. If a customer pays late, overdue invoices are collected in one list, and you can write a payment reminder that shows the amount still outstanding. The delivery status shows whether it arrived. Quotes can carry an expiry date, are written in your customer’s language and currency, and become an invoice once they are accepted. For regular work, recurring invoices are prepared on the due day, so you only check and release them.
Incoming documents are handled just as simply. Every account gets its own inbox for receiving e-invoices, which is free on every plan and has no volume limit. Paper and PDF receipts can be uploaded or forwarded by email. AI reads the amount, date, tax rate and supplier and assigns them to an expense. Warnings point out mismatches, so you can correct them before they cause problems. Assets can be depreciated by choosing a category, useful life and method, and the schedule is written for you.
Customer data is entered once, including address, tax number, language and currency, and every invoice for that customer reuses it. Time and costs can be collected on projects, and an invoice picks them up with one click. Revenue, expenses, profit and VAT are shown by month, quarter or year, and every figure can be exported.
For your tax advisor, BillingEngine exports invoices, expenses and payments as a finished DATEV booking batch. Bank statements can be imported in CAMT.053 format and matched with payments. Developers get a REST API with an OpenAPI description, and there is an MCP server that lets AI assistants work with your invoicing data.
BillingEngine is focused on the German market and is not a full double-entry accounting suite. Filing advance VAT returns through ELSTER is in preparation, and the figures for the return are already available in the application. A free e-invoice validator and viewer let you check and read e-invoices without an account.

What problem it solves

Since 2025, German businesses must be able to receive e-invoices, and sending them becomes mandatory step by step. Many small businesses still write invoices in Word or Excel, which don’t produce a valid e-invoice, and full accounting suites are often more than they need. BillingEngine lets them create compliant e-invoices (EN 16931) in a few clicks and receive them in their own inbox for free. It also removes the manual work around invoicing: receipts are read by AI, reminders and recurring invoices are prepared for them, and a finished DATEV export goes to the tax advisor.

Alternatives & competitors

sevDesk, Lexware Office (formerly lexoffice), easybill, Billomat, FastBill and Zoho Invoice. Compared with them, BillingEngine is lighter and focused on e-invoicing and simple bookkeeping for small businesses, with a free e-invoice inbox on every plan. The larger tools offer more integrations and a broader accounting scope.

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