Your tenant is two months behind on rent. You politely message them on WhatsApp: "Please transfer the outstanding amount." Silence. You file with the Bezirksgericht (district court). The tenant's lawyer argues your warning was formally defective — and the judge sends you back to square one. What many landlords in Austria don't know: for certain legal acts, WhatsApp does not replace the RSa-Brief, even if the tenant has demonstrably read it. This guide is written from the Austrian legal framework, because Camilia operates from Austria and that is the body of law that applies to it by default.

What Austrian courts require for a valid formal warning

To terminate a lease judicially for non-payment, § 1118 ABGB (Austrian Civil Code) requires a qualified warning: the landlord must give a reasonable additional payment period and expressly threaten termination. The court then checks whether this warning actually reached the tenant.

Here lies the crux: "reaching" under Austrian civil law means the message entered the recipient's sphere of control and they could, under normal circumstances, learn of it. An RSa-Brief (Rückschein zu eigenen Handen — personal-delivery receipt) proves this delivery via the tenant's signature. A WhatsApp does not prove it with legal certainty — the tenant could have lost the phone, uninstalled the app, or turned off read receipts.

When an RSa-Brief is legally mandatory

Austrian law directly or indirectly (through burden of proof) requires an RSa-Brief or notarial delivery in these cases:

- **Qualified warning before an eviction lawsuit** for non-payment (§ 1118 ABGB) - **Termination of a lease (Aufkündigung)** by the landlord for cause (§ 30 MRG) — must be written and filed with the court (§ 33 MRG, § 562 ZPO) - **Early termination of a fixed-term lease** outside contractual options - **Claims for contract breaches** that will later be litigated (damage, house-rules violations) - **Rent adjustments under an index clause**, if the contract requires written notice

An RSa-Brief in Austria costs about €3–5 and produces a Rückschein signed by the tenant. For especially sensitive deliveries, a notary can formally record the service.

When WhatsApp counts as evidence (and when it doesn't)

Austrian procedural law follows the principle of free evaluation of evidence (§ 272 ZPO). A judge may evaluate WhatsApp messages as documentary evidence (§ 292 ZPO by analogy). They are far from worthless — they can be decisive:

- As **complementary proof** that the tenant was aware of the default - As a **record of the dialogue**, if the tenant later alleges an installment agreement - As an **indication of good faith** from the landlord seeking an informal solution

But: for the **formal additional-period warning under § 1118 ABGB**, for the **Aufkündigung under § 33 MRG**, for **communications with full court-level evidentiary weight**, the RSa-Brief (or notarial service) is irreplaceable. WhatsApp complements — it does not replace.

The most common mistake: the landlord writes "no problem, pay next month" on WhatsApp, and the judge later treats it as an implicit deferral agreement. The default is diluted, the eviction delayed for months.

The correct procedural sequence for non-payment

Here is how an Austrian landlord should proceed when rent stops arriving:

1. **Initial neutral WhatsApp**: *"I have noted that rent for [MONTH] has not been received. Please transfer the outstanding amount within 7 days. This message does not constitute a waiver of contractual rights."* 2. **Export the full WhatsApp conversation** (with timestamps and read receipts) as evidence. 3. **RSa-Brief with qualified warning** under § 1118 ABGB: reasonable additional period (minimum 8 days, safely 14), explicit threat of termination, reference to § 30 MRG. 4. **Eviction lawsuit (Räumungsklage)** before the competent Bezirksgericht after the period expires unmet.

The WhatsApp record is attached to the lawsuit as documentary evidence — showing the tenant knew of the default and offered no serious solution. The RSa-Brief provides the formally valid warning. Together they form a complete evidentiary chain.

What you must never say on WhatsApp

As a landlord under Austrian law, systematically avoid:

- **"Don't worry" / "pay when you can"** — can be read as implicit deferral - **Vague promises** like "we'll figure something out" - **Waivers** of default interest (§ 1000 ABGB) or termination rights - **Installment acceptances** that are not in writing

Instead, use standard phrasings: *"This message is sent without prejudice. It does not constitute a waiver of contractual rights and creates no new agreement."* This is the Austrian equivalent of the Anglo-Saxon non-waiver clause — short, unobtrusive, legally effective.

GDPR and DSG 2018: keeping the WhatsApp history correctly

Storing WhatsApp history with the tenant is GDPR- and DSG-2018-compliant when the following apply:

- **Legal basis**: performance of the contract (art. 6(1)(b) GDPR) and legitimate interest (art. 6(1)(f) GDPR) in preserving evidence - **Retention**: 3 years after lease termination is reasonable (matches the § 1486 ABGB limitation period for rent claims) - **DPA with providers**: any software processing tenant data must sign a Data Processing Agreement under art. 28 GDPR - **Information duty**: mention in the lease that WhatsApp communications are documented and may be used in disputes

The Austrian DSG 2018 adds national rules (notably around the Data Protection Authority, DSB), but the core landlord duties match the EU standard.

How Camilia Casas automates the evidentiary path

Camilia Casas — the Camilia edition for long-term rentals — automates exactly this legal path:

- **When the tenant writes about payments, contract, deposit or eviction**, the AI **never** replies with friendly filler. It uses a procedural template with a non-waiver clause and alerts you immediately. - **Every message** (inbound and outbound) is stored with a SHA-256 hash chained to the previous message. Tampering breaks the chain detectably — a strong argument in court. - **When the case goes to the Bezirksgericht**, you export a **notarial dossier as PDF**: full chronology, HMAC signature of the chain tip, QR for public verification, verbatim references to MRG, ABGB, ZPO, eIDAS Regulation (EU) 910/2014 and GDPR. Your lawyer receives a directly usable document. - **The art. 28 GDPR DPA** is pre-signed with Camilia from the moment you activate your account.

Camilia replaces neither the RSa-Brief nor your lawyer. What Camilia does: make sure that **when the RSa-Brief has to be sent**, you already have six months of flawlessly documented WhatsApp evidence — showing the tenant knew what was coming and that you never informally agreed to a deferral.

Most Austrian landlords lose months in the eviction procedure — not because the law is complex, but because in the first WhatsApp messages they were polite enough to create an implicit deferral. The rule is simple: **communicate informally, draft procedurally**, archive every conversation with cryptographic integrity, and for formal warnings always rely on an RSa-Brief or notarial service. Camilia Casas automates this for €9 per door per month — if you do it manually, you now know what to watch for. This guide is general information and does not replace legal advice; for your specific case consult an Austrian Rechtsanwalt.