Text messages

Your dunning letter is in an inbox. The text was read an hour ago.

DunningHero can back every level with a short text message: same case, same schedule, on the one channel your customer actually holds in their hand.

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2Email or letter goes out
3The text follows

What your customer sees

Muster GmbH: invoice RE-2026-0041 for €1,485.00 is overdue. Details are in our email.

85 / 160

The default wording, overridable per level. No marketing, no link, no threat — just the case.

Reach

Why a text lands where the third email does not.

Two grades of evidence sit side by side here, and we say which is which.

22.8%

of B2B emails opened

Inxmail benchmark 2026, across 4 billion emails. Four in five are never opened at all.

~98%

of texts opened

Figures published by SMS providers, not an independent study. The order of magnitude is consistent across vendors — sources are linked below.

3 min

typical time to read

Provider figures again. For dunning, one thing follows: a text works the same day, not the following week.

How it works

The text announces. The document stays the document.

160 characters can’t carry a full dunning text — but they make sure the dunning letter gets read.

1
A level comes due
Your rules decide when, exactly as before. The text hangs off the level; it is not a level of its own.
2
Email or letter goes out
With the full text, the dunning fee, the deadline and the PDF. That is the Mahnung and stays the Mahnung.
3
The text follows
Short and factual, with the invoice number and the amount — and where to find the details.
4
Payment stops both
Once the amount is settled in your accounting system, the next sync ends the chain. The texts with it.

Channels

Each channel does something the others cannot.

Channels	Email	SMS	Letter
Reach	Roughly a quarter get opened; the rest sit unread or land in spam.	Almost every delivered text is opened (provider figures).	Physically on the table, and hard to overlook.
Speed	Minutes to days, depending on when someone checks.	Minutes. The phone is in a pocket, not on a desk.	Two to three working days, printing and post included.
Legal weight	Carries the full dunning text with fee, deadline and PDF.	Valid as a dunning notice in principle — no form is required (OLG Hamm, I-4 U 252/22) — but receipt is hard to prove. So our text only announces the dunning letter.	The letter with the full dunning text — the basis for default and the court procedure that may follow.
Cost per send	Included in every plan.	Add-on, as a monthly bundle of 50, 250, 1,000 or 5,000 texts.	Add-on: €2.50 per letter, €6.00 as an Einwurf-Einschreiben (net).
Best for	The default route for every level.	When emails go unanswered — private customers above all.	Late levels, and customers with no reliable email address.

Email

Reach: Roughly a quarter get opened; the rest sit unread or land in spam.
Speed: Minutes to days, depending on when someone checks.
Legal weight: Carries the full dunning text with fee, deadline and PDF.
Cost per send: Included in every plan.
Best for: The default route for every level.

SMS

Reach: Almost every delivered text is opened (provider figures).
Speed: Minutes. The phone is in a pocket, not on a desk.
Legal weight: Valid as a dunning notice in principle — no form is required (OLG Hamm, I-4 U 252/22) — but receipt is hard to prove. So our text only announces the dunning letter.
Cost per send: Add-on, as a monthly bundle of 50, 250, 1,000 or 5,000 texts.
Best for: When emails go unanswered — private customers above all.

Letter

Reach: Physically on the table, and hard to overlook.
Speed: Two to three working days, printing and post included.
Legal weight: The letter with the full dunning text — the basis for default and the court procedure that may follow.
Cost per send: Add-on: €2.50 per letter, €6.00 as an Einwurf-Einschreiben (net).
Best for: Late levels, and customers with no reliable email address.

You can combine all three, for example: email always, a text from level 2, a letter from the first dunning level.

The frame

A text to your customer is not a newsletter.

It concerns a live case between you and your customer. It still deserves to be set up properly.

Only about their own invoice

Texts go only to customers with an open invoice, about that invoice. We send no advertising, and you cannot send any through us.

Per level, pausable any time

You decide per level whether a text rides along. Single cases and whole customers pause or are excluded as usual.

Your wording, your sender

Your own text per level and your company name as the sender. The character counter shows how many segments a message needs before it goes.

No number, no text

If your accounting system holds no mobile number, the text is skipped silently — the level itself still goes out.

FAQ

What businesses ask before their first text goes out.

Am I allowed to send a payment reminder by text at all?

In principle, yes: the OLG Hamm held payment requests by text message to be permissible for justified claims (judgment of 07.05.2024, I-4 U 252/22). This is an existing contract and an open invoice, not advertising. If a claim is disputed, pause the case — then no text goes out either. If you are unsure, run it past your lawyer; we supply the mechanism, not the legal advice.

Does the text replace the dunning letter?

No. Legally a text can be a dunning notice, but its receipt is hard to prove — and the fee, the deadline and the full wording belong on a document. That is why a level only counts as sent here once the email or letter is out; a text alone never moves the case forward.

Where does the mobile number come from?

From your accounting system. We pick it up on sync from Lexware Office, sevDesk, FastBill or Papierkram and put it into international format; if you use HERO Software or ToolTime, it comes from Lexware Office. Anything that cannot be dialled — an extension, a note — is discarded rather than guessed at.

What does sending a text cost?

SMS is an add-on with monthly bundles of 50, 250, 1,000 or 5,000 messages; whatever is left at the end of a month does not roll over. The editor shows how many segments your text makes as you write: up to 160 characters is one, up to 306 is two. We do not send longer texts.

Can a text remind before the due date?

Yes, if you switch it on — it is off by default. A single text then goes out a chosen number of days before the due date (1 to 14, default 3), and only if the invoice is still open: once per invoice, never retried, Monday to Friday between 8 am and 8 pm in your time zone. It needs the SMS add-on and activated sending.

Sources

Checked in September 2026. The email figures come from named studies with a stated data base, the SMS figures from providers' own data — we label the difference, because the two do not carry the same weight. The legal assessment rests on the OLG Hamm judgment.

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