The cobbler's children have no shoes
I'm Christian, the founder of To Bill. I also run a sole proprietorship in Geneva, Fast Digital, which is not registered for VAT. Its books are kept in To Bill, of course. And in October 2026, I had to admit it: they were full of mistakes.
Not fraud. Ordinary mistakes, the kind you make when you do your books in the evening, between two projects, telling yourself you'll take a closer look later.
I asked Claude, Anthropic's AI assistant, to sort them out. It worked in To Bill, with me: it read the books, explained what it found, proposed the correction, and I decided. Here is what it found. I give no amounts from my business here: just the number and the kind of mistakes, because they are what matters.
What the AI found in my books
A client payment counted twice
The same client payment appeared twice in my revenue. My turnover was inflated by that much, and nothing flagged it at a glance: both entries looked perfectly normal.
The duplicate was corrected. In To Bill, a posted entry is never deleted: it is reversed, and the trace of the mistake stays in the journal.
Seven receipts booked a second time
Seven expenses had been booked from their receipt, then a second time from the bank line of their payment. My expenses counted seven purchases too many.
The right practice is simple: an expense already booked is matched to its bank line, not booked again.
Private spending “ignored” instead of account 2850
A few private expenses had been paid from the business account. During reconciliation, I had marked them “ignored”, as if they did not exist.
But in a sole proprietorship, a private expense paid from the business account is still a movement of that account. It is booked to the private account, 2850. Ignoring it lets the bank account in the books drift away from the statement.
TWINT payments on the wrong account
TWINT payments received on my personal account had been recorded on the business bank account. So my books showed, on the business bank, money that never arrived there. The correction took them out of that account.
Refunds treated as discounts
Refunds from Infomaniak had been booked as purchase discounts. A refund is not a discount: it cancels the purchase it refunds. The difference may not show in a total, but it distorts the detail of your expenses.
VAT without VAT registration
The instalments financing my laptop had been booked as an expense, with VAT. Two mistakes in one. Fast Digital is not registered for VAT, so there is no input tax to reclaim. And an instalment repays a loan: it reduces a debt on the balance sheet, it is not an expense.
Bank rules learned the wrong way
To Bill's bank rules propose an account for each new statement line. Mine had learned from my old chart of accounts, a home-made one. Every new line inherited the mistake. The rules themselves had to be corrected, on top of the entries.
A gap of 1.42 francs
At the end, there was a gap of 1.42 francs between the general ledger and the bank. A trifle? No: a gap, however small, says that something is wrong. Claude tracked it down. Some expenses had been booked at the receipt amount, not at the amount the bank actually debited. For a bank account, the statement is the truth.
The result
| What was done | How many |
|---|---|
| Bank lines reconciled | about 200 |
| Client payment counted twice | 1, corrected |
| Receipts booked a second time | 7, corrected |
| Books health score | from 80 to 88 |
To Bill's books health score, which sums up the consistency checks of the accounts, went from 80 to 88.
Every mistake became an improvement
What strikes me most is that my mistakes are nothing exotic. They are those of many freelancers: duplicates, private items in the wrong place, VAT where it has no business, receipt amounts instead of the bank amount.
Every correction became an improvement of To Bill, for every customer. You find their spirit in the rules To Bill now gives any assistant connected to it: correct with a reversal or a new entry, book a sole proprietorship's private items to account 2850 rather than ignoring them, book no VAT for a company that is not registered for it, and treat the bank statement as the truth for bank accounts.
Your turn, with your own Claude or ChatGPT
I did this clean-up with Claude working in To Bill. Since 18 October 2026, To Bill's MCP connector lets every customer do the same from their own Claude or ChatGPT:
- Add the address
https://app.tobill.ch/mcpin your assistant (on claude.ai: Customize › Connectors › Add custom connector; in ChatGPT, in developer mode). - Allow your company on To Bill's page, “Read only” or “Read and modify”.
- Ask it: “Sort out my books”.
It never has more rights than you, it asks for your approval before every change, and every entry it books shows your name followed by its own, for example “via Claude”. You cut off access whenever you like, in Settings › AI and API connections. Each assistant, step by step, is in the guide Connect Claude, ChatGPT or another AI assistant, and what the assistant receives is explained on the AI in To Bill page.
Two tips to finish. Start with “Read only”: you will see what it finds before you let it correct anything. And keep your fiduciary in the loop: To Bill's accounting is still an experimental feature, and an AI does not replace a professional's eye before you file a return.
Christian Da Silva, founder of To Bill