Security & data protection
Your client records. Clear controls.
Before a tax firm entrusts bookkeeping to AI, it needs to know where the data goes, who can access it and how a result can be checked. Here is how DeinHans is built around those questions.
Updated: 7 October 2026
Separate client workspaces
Company access is checked on the server.
Evidence behind the result
Source, proposal, review and correction stay connected.
Your firm keeps control
Review rules and professional acceptance remain distinct.
01 · GDPR & professional secrecy
Know who is responsible for each data flow.
Client bookkeeping and running our own business are different processing purposes. They require clear roles and agreements.
Your bookkeeping data
When DeinHans processes client documents under your instructions, the instructing customer is the controller and DeinHans is a processor. The Article 28 data processing agreement (DPA) must cover the purpose, data categories, duration, instructions and subprocessors.
Your relationship with DeinHans
DeinHans acts as controller for its own enquiries, account administration, billing and platform-security records. A tax firm acting under its own professional mandate generally remains an independent controller for that work.
Client confidentiality needs its own protection.
For German tax firms, a DPA alone is not the whole assessment. Section 203 StGB and section 62a StBerG also matter: necessary access only, carefully selected service providers, confidentiality commitments and controls over further providers. Overseas processing requires a separate assessment of professional secrecy as well as GDPR transfer safeguards.
Before live client records are processed, agree the DPA, technical and organisational measures (TOMs), provider list and confidentiality terms. A privacy notice explains processing; it does not replace those agreements.
02 · GoBD & auditability
Support GoBD. Trace every bookkeeping step.
DeinHans supports GoBD-compliant bookkeeping with linked source documents, recorded decisions, protected postings and traceable corrections. Your firm can follow the evidence through to the monthly export.
Original evidence
Document or bank source, with a file fingerprint and company context.
Prepared treatment
Extracted facts, allocations, proposal and unresolved questions.
Review & posting
Recorded approval and posting actions within the configured workflow.
Correction & export
Linked reversals or adjustments and the monthly export for onward work.
Corrections leave a trail
Posted journal entries are protected against ordinary rewriting. Corrections use controlled reversal or adjustment paths. Audit records retain the action, actor and time.
Closed periods have boundaries
Posting and financial changes are checked against period locks. An unresolved case remains distinguishable from a posted result.
Exports are part of the handover
DATEV exports support onward processing. Your firm should verify mapping, completeness, readable evidence and the destination archive as part of its agreed workflow.
GoBD compliance concerns the whole process.
GoBD also applies to upstream systems and their interfaces. Complete and timely recording, statutory retention, backups and your process documentation therefore belong to the agreed end-to-end workflow. DeinHans does not replace a separately commissioned long-term archive. A DATEV export alone does not automatically contain every record and history required for a tax audit. These controls are not an official certification or a blanket assurance for every customer workflow.
03 · AI & human oversight
AI does the preparation. Your firm makes the professional decisions.
AI can read documents and help resolve bookkeeping cases. Its output enters a controlled accounting workflow with validation, visible exceptions and approval rules; it is not professional sign-off.
What reaches an AI service?
Depending on the task, document text, PDFs or images, transaction details and relevant company or case context. These can contain personal data. AI processing is not described as anonymous, and it is separate from advertising measurement.
What can the reviewer inspect?
The source document, proposal, payment allocation and flags. Cases requiring individual approval are separated from usable proposals eligible for bulk confirmation. Missing or invalid results still require resolution.
OpenAI API
Used through the direct API for document extraction and specialist analysis. Voluntary sharing for general-purpose model training is disabled. The operator confirms that logging is disabled in the production account. Remaining retention depends on the endpoint and provider rules; this does not establish formal zero retention or exclusively European processing.
OpenAI data controlsOpenRouter
The associated accountant-agent feature is currently disabled. OpenRouter is not an approved recipient of client data for the agreed firm service. Activation would require prior inclusion of the actual providers and data flows.
OpenRouter retention controlsDeinHans does not use customer bookkeeping content to train general-purpose AI models or for unrelated advertising. Processing results and relevant decision history can still be retained inside DeinHans for the bookkeeping workflow.
What the EU AI Act means here
The intended use is bookkeeping preparation and review support. The applicable AI Act duties depend on that intended use and the role of each party. Using an external model does not transfer all duties to its vendor. For a firm, practical controls include knowing where AI is used, giving staff suitable AI literacy, checking limitations and keeping competent human oversight.
This page does not claim an AI Act certification or a completed high-risk conformity assessment. A materially different use, such as decisions about credit or employment, needs a fresh assessment. The agreed service remains bookkeeping software; tax advice, filings and professional acceptance stay with the responsible professional.
04 · Providers & data flows
Which services handle which information?
A booking request and an uploaded client invoice do not follow the same route. This overview distinguishes product processing from billing, communication and website operation. It is not a substitute for the deployment-specific subprocessor annex.
| Service | Purpose | Data involved |
|---|---|---|
| Supabase | Product database, authentication and file storage | Accounts, organisation membership, bookkeeping records, uploaded evidence and processing history. |
| Railway | Backend API and background processing | Documents and bookkeeping context processed by the application, job state and operational logs. |
| Vercel | Website, web application and request transport | Page requests, request metadata and application data passing through server routes. |
| OpenAI | Document extraction and specialist AI analysis | Task-specific documents, images, extracted text and accounting context. |
| Stripe | DeinHans subscription billing | Billing contact, payment-method collection, invoices and subscription status. DeinHans does not store full card details. |
| Cal.com | Scheduling calls | Contact details, appointment information, meeting links and booking status. |
| Notion | Enquiry and relationship management | Contact details, business-fit information, submitted messages and CRM notes. It is not the product’s bookkeeping store. |
| Resend | Transactional and service emails | Recipients, message content and delivery status for account, invitation and service communication. |
Cloudflare protects public forms. Google sign-in is optional where enabled; Google and Meta measurement on public pages requires the relevant consent. These website functions are explained in the privacy and cookie notices.
Your connected sources
If you choose a Google Drive import, folder and file identifiers, metadata and selected files are processed between Google and DeinHans. Source sharing permissions need a separate check. Do not make confidential client folders publicly accessible to enable an import.
Where is the data processed?
Our primary production database is hosted in Frankfurt, Germany. That location does not cover every processing step: AI services, support and logs can involve other countries. The OpenAI project inspected on 28 September 2026 uses Global residency. The provider annex must identify the services, processing locations and transfer safeguards that apply to your agreed service.
05 · Access & operations
Access follows a role and a company.
Server-checked access
The backend checks authentication, company membership and the permission needed for an action. Selecting a company in the interface does not itself grant access to its records.
Protected document previews
Document preview routes check access before creating time-limited signed links. A signed link remains sensitive while valid and should not be forwarded outside the authorised team.
Support access under your control
Product access through support@deinhans.de requires support access to be enabled for the relevant organisation. Authorised people in your organisation or firm can manage and revoke it. Support cannot grant its own access. Authorised staff access records only for the agreed support purpose and subject to confidentiality. Technical infrastructure access is managed separately. For new organisations, this beta support setting is currently enabled by default; authorised people can switch it off.
Operational safeguards
Transport encryption, restricted service credentials, company access checks and operational logging support the service. Recovery targets and incident contacts belong in the agreed service documents.
Database backups and document recovery
Our production database is backed up daily; the current Supabase Pro plan provides seven days of recovery history. These backups do not contain uploaded PDF, image or XML files. A regularly operated separate file backup with a verified recovery path has not yet been evidenced. Statutory long-term retention and a recovery SLA are not promised by this arrangement.
A concern about data or access?
Contact hello@deinhans.de with the affected account, approximate time and a short description. Do not send passwords or attach client records to the initial message. For a personal-data breach, controller and processor notification duties follow the GDPR and the DPA; processor notification to the controller is required without undue delay.
hello@deinhans.de06 · Retention, deletion & exit
Keep required records. Delete data without a continuing purpose.
Closing an account does not make every bookkeeping record deletable, and GoBD is not a reason to keep everything indefinitely. The decision depends on the record, the applicable obligation and the controller’s instructions.
Books and annual records
For example, accounting books, inventories, opening balance sheets and annual financial statements.
Booking vouchers
For example, invoices and receipts that support bookings.
Relevant correspondence
Commercial or business correspondence and other records where the statutory rule applies.
These are common statutory periods, not a DeinHans storage-plan promise. Periods generally start at the end of the relevant calendar year; audits, legal holds and special rules can extend them.
The privacy workflow separates deletion from justified restriction: verify the request, identify affected records, review retention grounds, approve actions and verify the result. Unused uploads, account data and marketing records need their own decisions. Removing one user must not erase a shared company’s books.
Agree the exit before you need it.
Your agreement should specify export scope, the export window, archive responsibility, deletion of active data and the backup lifecycle. Provider follow-up is separate from deletion in our database. This page does not promise instant deletion from all providers or backups.
Send access, correction, deletion or objection requests to hello@deinhans.de. Requests are normally answered within one calendar month, subject to the lawful extension rules. Where we act as processor, we assist the responsible controller.
07 · Before going live
Review the documents and a complete workflow.
Use these four checks to assess DeinHans for your firm. Current demonstrations use synthetic example documents while we complete the contractual and operational setup for real client records.
Agree the processing terms
DPA, TOMs, confidentiality commitments, active subprocessors, locations and transfer safeguards.
Define the firm’s controls
Who can upload, answer business questions, change rules, approve, export and administer access.
Inspect a complete case
Follow a source through a proposal, exception, approval and correction. Check the monthly export in your existing accounting process.
Set retention and incident arrangements
Record retention periods, archive and backup responsibilities, exit arrangements and the contact path for incidents and rights requests.
We will discuss the applicable documents and open questions with you before you decide to use live client data. Public product descriptions do not replace the agreed service, DPA or your firm’s documented assessment.