In many online sellers’ books, the “accounting” cost centre shows a reassuring number: zero euros. No service provider, no software – it is done in-house. But that zero is an optical illusion. It exists because the company’s most expensive resource never appears on any invoice: the founder’s own hours.

This article does the maths – with realistic assumptions rather than shock figures – and shows at which order volume manual bookkeeping turns from a saving into a growth brake.

The base calculation: minutes × documents × hourly rate

A single document seems harmless: download the invoice, rename it, file it, match it to the payment, enter it into the books. A practised hand manages that in about two minutes. The impact comes from multiplication:

Orders/month	Time (2 min/doc)	Cost at €25/h	Per year
500	≈ 16.7 h	≈ €417	≈ €5,000
2,000	≈ 66.7 h	≈ €1,667	≈ €20,000
5,000	≈ 166.7 h	≈ €4,167	≈ €50,000

Even the €25 hourly rate is conservative: it reflects an assistant rather than the owner, whose hour generates a multiple of that in sourcing, marketing or product work. And two minutes covers the standard case – not the PayPal order with a partial refund, or the Amazon settlement with fourteen fee types.

The second layer: error costs and advisor queries

Manual processes do not just scale badly – they get more error-prone under load. Every misassigned document shows up twice later: as a query from the tax advisor (whose hour costs far more than €25), as search time at month-end, and in the worst case as a correction after the GoBD monthly lock – meaning a documented reversal.

Add the calendar effect: bookkeeping done “in between” drifts into evenings and weekends – or piles up until the VAT return deadline forces it. The most common consequences are covered in our article on avoiding accounting mistakes.

The third layer: opportunity cost

The real question is not “what does bookkeeping cost me?” but “what could the same time earn elsewhere?” 66 hours a month is two full working weeks – enough for a new product line, a second marketplace, or simply: weekends. Growth requires freeing those hours; investing them in document filing means subsidising routine with entrepreneur time.

Run your own numbers

Generic figures convince no one – your own figure does. With the free Manual Accounting Cost Calculator you get your personal calculation in a minute: enter order volume, minutes per document and hourly rate, and read the result per month and year. The output is deliberately a lower bound – error costs and advisor queries come on top in reality.

Two reference points for the input: if you only file and match invoices, 1–2 minutes per document is realistic; if you also reconcile payments and transfer everything into DATEV, expect 3–5 minutes.

Automate, outsource – or both?

Outsourcing moves the work; automation removes it. Fetching documents from marketplaces, matching them to payments and producing a clean, structured export for your tax advisor are textbook examples of tasks software does more reliably than people – around the clock, without slips of concentration. Your tax advisor keeps doing what they are irreplaceable for: professional judgement instead of data entry. Our article on automated accounting for online sellers sketches what that shift looks like.

Conclusion: the zero in the cost centre is an illusion

Manual accounting has a price – not on an invoice, but in hours, errors and forgone growth. Make the number visible: open the Manual Accounting Cost Calculator, enter three values, read the annual total.

And if that number stings: KudTax automates exactly the work you just priced – invoices and transactions from Amazon, eBay, Shopify, PayPal & co. are fetched automatically, matched by AI, and handed to DATEV ready to book. 66 hours of document work become one review at month-end.

The True Cost of Manual Accounting: The Hours Nobody Books