Accounts receivable automation for a small business does not mean reminders go out on their own. It means overdue invoices get spotted on a schedule, the next step, from friendly reminder to formal notice, is drafted at the right moment, and the wording sounds like you. On top of your accounting software, AI adds three things: drafts in your own voice, matching open invoices against incoming payments, and preparing the facts when a client pushes back. Whether to chase, how firmly, and when friendly is over stays your call. Whether that pays off depends on how many invoices you send; for me it doesn't.
This isn't legal advice, just the operator's perspective from running my business with fourteen AI employees. The legal side below is German law, based on the wording of the German Civil Code (BGB) as retrieved on 28 October 2026; where I interpret it, I say so. If you invoice under another country's law, the workflow carries over, the deadlines and amounts do not. How a single reminder email is built is covered in Writing Business Emails: With or Without AI, a ready-made template in Business Email Templates That Work.
The process: from unpaid invoice to final notice
Stage 3 matters most: chasing a paid invoice costs goodwill.
What German law says about default, interest and the flat fee
The core rule is section 286(1) BGB: if the debtor does not pay after a reminder from the creditor made after the due date, the reminder puts them in default. The section does not care what you call the letter and requires no deadline. Whether your friendly payment reminder already counts as that reminder depends on how it is worded; the stage names in the table above are common usage, not law.
No reminder is needed under section 286(2) no. 1 BGB where a time for payment is fixed by the calendar, meaning a validly fixed date such as an agreed payment date; a date you put on the invoice on your own does not automatically do that. Independently, section 286(3) BGB says the debtor of a payment claim is in default at the latest if they do not pay within 30 days of the due date and receipt of an invoice. Against consumers, that only applies if the invoice pointed out this consequence specifically. So that notice belongs in your invoice template, not in the reminder.
Once in default, section 288(1) BGB sets interest at five percentage points above the base rate per year; where no consumer is involved, section 288(2) sets nine percentage points for payment claims. The Deutsche Bundesbank publishes the current base rate under section 247(2) BGB. On top of that, section 288(5) gives a claim to a flat fee of 40 euros where the debtor is not a consumer, credited against any damages for legal costs.
The statute names no fixed "reminder fee"; section 288(4) only says that claiming further damage is not excluded. Whether your fee falls under that is a question for a professional.
Accounts receivable automation: what your accounting software already does
My invoices come from Lexware Office, a German accounting tool, where Anton, my AI employee for quotes and invoices, creates them as drafts once a client says yes; I approve and send. According to Lexware's help pages, the software already handles:
- Showing what is overdue. Its document list has views for overdue and open documents, and overdue ones are flagged in orange.
- Creating the reminder from the invoice. A "remind" action on the invoice produces the document directly.
- Saving your wording. Title and opening text can be stored as defaults, friendly or firm.
- Adding a reminder fee as a line item, optionally, and sending by email or post.
The same page also notes: the remind action only exists for invoices created in Lexware Office, editing a reminded invoice deletes its reminder history, and there is no automatic sending; every reminder, including a partial one after a part payment, is triggered by hand. Via the API, dunning notices are always created as drafts, according to Lexware's developer docs; connecting an AI role is covered in Lexoffice Integration: The Main Routes. For other tools, there is an overview in Accounting Software for Small Businesses.
Where AI fits into the dunning process
1. Match open items before anyone gets a reminder
You hand over two exports: your open invoices and your bank transactions since the oldest open date. The AI matches them by amount, invoice number in the payment reference and name, and puts each invoice in one of three piles: paid, open, unclear. Unclear is anything that does not match cleanly, such as a part payment.
Peter, my AI employee for receipts and bookkeeping, matches incoming receipts against credit card statements in my business, not invoices against payments. Items that do not match cleanly he does not force to fit, he reports them as open. That rule belongs in any matching run before a reminder.
2. Drafts in your own voice
Each stage needs a text that sounds like you, not like a collection agency. Sonja, who writes the email in my voice, learned my tone from 50 of my real sent emails and puts drafts in my inbox; nothing goes out until I say so explicitly. Her job is new-client emails, not reminders, but the method transfers. More on that in Can AI Write Emails in My Voice?.
3. Prepare the facts when a client pushes back
If a client replies "I never got that invoice" or "the work wasn't finished", the run stops there. The AI pulls together the invoice, the quote, the delivery date and the email thread and sums up the issue in three sentences. You get a draft reply with it, not a decision.
A brief for stages 3 and 4, structured like my prompt templates:
Goal: Open invoices with a status, and a draft payment reminder for
each open one. I review and send myself.
Context: I run <business>, tone <formal/informal>, friendly and
direct. How I sound: "<sentence 1>" "<sentence 2>"
Material: Open invoices: <export>. Bank transactions since <date>:
<export>. Do not remind: <clients>.
Limits:
- You send nothing.
- Only match a payment if amount and invoice number or name match
clearly, otherwise status "unclear" with the reason.
- No interest, fees or flat charges.
Format: Table of invoice number, client, amount, overdue since, status
(paid/open/unclear). Below it, a draft per open invoice: subject with
number and date, six sentences at most, new date.
Done when: Every invoice has a status, and no draft concerns "paid"
or "unclear".
Before real client data goes in, read AI and Privacy: What the AI Gets to See.
Where you decide
How this works in my business, and when automating pays off
My own dunning is not automated. I don't have that many invoices, and I have a very personal relationship with my clients. So the first reminder is always personal, and I have only had to send a proper formal notice a handful of times. So you don't have to automate everything, even if you could. As a developer, the rule was always: no over-engineering.
Rule of thumb: as long as you keep your open invoices in your head and know your clients personally, a message you write yourself is the better route. The process above only pays off once so many invoices are open that it could save you hours. Always weigh cost against benefit.
Frequently asked questions
Can you fully automate accounts receivable?
The spotting and preparing, yes; the deciding, no. Whether a client gets a reminder, with which deadline and what happens after the final notice stays with you.
How many reminders do I have to send?
German law sets no number. Section 286(1) BGB speaks of one reminder. Three stages are a habit, not a requirement. When to apply for a court payment order instead is a decision to make with a professional.
What do I do about a part payment?
It goes on the "unclear" pile, not "paid". Whether the gap is a mistake, a deduction over a complaint or an agreed instalment, you clarify with a question, not a reminder. Chasing the rest is a partial reminder in Lexware Office, according to its help pages, triggered only by hand.
Can an AI send reminders on its own?
In my business, none of the roles that draft for clients sends on its own: Anton, Sonja and Frieda create drafts, I send. That goes double for reminders: a wrong one to a client who paid can't be taken back.
Where to go from here
First count how many invoices stay unpaid each month. If it's a few and you know your clients personally, write the first reminder yourself, as I do. Otherwise export your open invoices and recent bank transactions and have them matched once, without sending anything. Then write down your stage rule: days per stage, tone, new deadline, exempt clients.
More workflows that split up this way are collected under Process Optimization. If you get stuck, bring your process to my community Claude Practitioners; Anton and Sonja are there as ready-made packages, with the course.
