Lexware Office (lexoffice) Integration Research

Date: 2026-03-31 Status: Initial Research Complete — Key Uncertainties Remain

Table of Contents

1. Summary
2. Capability Matrix
3. System Overview
4. Integration Intermediaries & Middleware
5. Authentication & Connectivity
6. Invoice/Document Submission
7. Master Data Access
8. Historical Bookings / Journal Entries
9. Status & Feedback
10. Unresolved Questions
11. Suggested Hands-On Testing Plan
12. Dead Ends
13. Sources
14. Retractions

Summary

Lexware Office (formerly lexoffice) is a cloud-based accounting platform by Haufe Group, widely used by German SMEs, freelancers, and their tax advisors. It provides a REST API (Public API and Partner API) with endpoints for contacts, invoices, vouchers, files, posting categories, and webhooks.

The central challenge for Orcha's AP automation use case is that voucher creation via the API is restricted to sales voucher types (salesinvoice, salescreditnote). Expense vouchers (purchaseinvoice, purchasecreditnote) — which are the voucher types Orcha needs to create — are read-only via the Public API. The official bookkeeping cookbook states this explicitly. Three alternative paths exist for submitting incoming invoices: (1) uploading files via POST /v1/files with type=voucher, which places the document in lexoffice's receipt capture inbox for semi-automatic OCR processing; (2) using Maesn's unified API, which is an official Lexware Technology Partner and offers a bills endpoint that may abstract over this limitation; (3) email forwarding to a dedicated lexoffice inbox address.

Master data access is partially available: contacts (customers/suppliers) support full CRUD, and posting categories (lexoffice's equivalent of a chart of accounts) are readable. However, there is no cost center endpoint, and no journal entries endpoint in the native API. Maesn's unified API does offer journal entries, chart of accounts, and suppliers endpoints that could bridge some of these gaps.

Capability Matrix

1. System Overview

What is Lexware Office?

"Lexware Office is one of the most widely used accounting and financial management systems in Germany, particularly popular among small and medium-sized businesses, accountants, and tax professionals." — Maesn Blog

Confidence: High

• Vendor: Haufe Group (brand: Lexware)
• Type: Cloud-based accounting SaaS
• Market: German SMEs, freelancers, tax advisors
• Rebranding: "lexoffice" was rebranded to "Lexware Office" in ~2025. The API gateway migrated from api.lexoffice.io to api.lexware.io. Both may still function.
• Pricing tiers (net/month, regular price):
  • S: EUR 7.90
  • M: EUR 12.90
  • L: EUR 21.90
  • XL: EUR 32.90 (required for API access)

"API access is only available for users with the XL plan" — GetApp/Capterra reviews

"Developers can use Lexware's free trial environment, which mirrors the functionality of the highest pricing tier – the XL plan" — Rollout

API Architecture

• Type: REST API, JSON request/response
• Base URL: https://api.lexware.io (new), https://api.lexoffice.io (legacy, may still work)
• Versioning: /v1/ prefix, no explicit version numbering beyond this
• Date format: RFC 3339/ISO 8601 (yyyy-MM-ddTHH:mm:ss.SSSXXX)

Available Endpoint Categories (Public + Partner API)

Articles, Cash Boxes (Partner), Contacts, Countries, Credit Notes, Delivery Notes, Down Payment Invoices, Dunnings, Event Subscriptions, Files, Finance (Partner — financial accounts/transactions), Invoices, Order Confirmations, Organization, Partner Integrations, Payment Conditions, Payments, Posting Categories, Print Layouts, Profile, Quotations, Recurring Templates, Transaction Assignment Hint, Voucherlist, Vouchers.

2. Integration Intermediaries & Middleware

Maesn (Recommended Investigation Path)

"Maesn is an official Lexware Technology Partner." — Maesn Integrations

"A single connection to the Maesn API is sufficient — they handle the mapping and communication with the target systems." — Maesn

Maesn's Unified API endpoints for accounting:

• Bills (create, retrieve, update, delete, line items, documents)
• Invoices (create, retrieve, patch, line items, documents)
• Expenses (create, retrieve)
• Contacts (create, retrieve, patch, bulk create)
• Suppliers (create, retrieve, patch)
• Customers (create, retrieve, patch)
• Chart of Accounts / Accounts (create, retrieve)
• Journal Entries (create, retrieve, bulk create, attachments)
• Tax Rates (retrieve)
• Payment Terms (create, retrieve)
• Payments (create, retrieve, delete)
• Fiscal Year info
• Open Items
• Webhooks
• File uploads
• Booking proposals

"When you work through Maesn, these calls are combined and automated within their unified API, so your integration experience this as one seamless operation rather than a multi-call sequence." — Maesn Blog

Passthrough capability: Maesn offers authenticated passthrough to the underlying lexoffice API.

"The baseUrl is set to https://api.lexoffice.io/v1/" and "only include the part after this base in the path field" — Maesn Passthrough Docs

Critical question: Does Maesn's bills endpoint successfully create purchase invoices in lexoffice despite the native API's read-only restriction on expense vouchers? Maesn may use the file upload path or have Partner API access that circumvents this. This is the highest-priority item to verify hands-on.

Pricing: Free tier for 30 days with test data; SCALE tier pricing not publicly listed (contact sales). Maesn already has a relationship with Orcha for the DATEV integration.

Confidence: Medium — Maesn clearly supports lexoffice as a system, and lists bills as an endpoint, but whether bill creation works for lexoffice specifically (given the underlying API limitation) is unverified.

Chift

"Lexware Office is classified under Chift's accounting integrations category" and is listed as "Live" — Chift Lexware Office

Chift offers a Unified Accounting API that includes lexoffice. They claim to support pulling accounts receivable and accounts payable, and automating invoice capture and reconciliation.

"The API automates data transfer between invoicing or ERP software and accounting software" — Chift Blog

Limitation: Specific operations supported for lexoffice (which endpoints, read vs write) are not documented on the public Chift website. Would need to request access to their developer docs or book a demo.

Confidence: Low — Chift lists lexoffice as supported, but zero specifics about what operations are available for this particular integration.

Celigo

No dedicated lexoffice connector found. Celigo has 300+ connectors but lexoffice is not among the named ones. Universal connector could be used for custom integration.

Confidence: High (that no connector exists)

Make.com (Integromat)

Make.com has a Lexware Office connector with:

• Watch Events (webhook trigger)
• Upload a Document (for bookkeeping)
• Create a Voucher
• Upload a File to a Voucher
• Search/List Vouchers
• Contact CRUD
• Invoice retrieval and PDF rendering
• Generic "Make an API Call" action

Confidence: High — Well documented on Make.com Apps

Other Platforms

• Zapier: Has lexoffice integration for triggers and actions
• n8n: Community node exists
• Pipedream: Has lexoffice integration
• Synesty: Has lexoffice add-on, but voucher creation limited to salesinvoice and salescreditnote

3. Authentication & Connectivity

Public API — API Key

"Navigate to Extensions, Weitere Apps, Public API or open Lexware Developer Portal directly and create a new API key with the desired permissions." — Microsoft Learn Connector

• User generates an API key in their Lexware Office account
• Key is used as Bearer token: Authorization: Bearer {accessToken}
• Scopes are selected at key generation time
• Simple but requires customer action

Confidence: High

Partner API — OAuth 2.1

"Partners receive unique client-id and client-secret credentials" — Lexware Partner API Docs

• Authorization URL: https://app.lexoffice.de/oauth2/authorize
• Token URL: https://app.lexoffice.de/oauth2/token
• Revocation: /oauth2/revoke
• Flow: Authorization Code with PKCE
• Token refresh: POST with grant_type=refresh_token
• Scopes: Resource-specific patterns (e.g., vouchers.read, vouchers.write, group.cashbox)
• Requirement: Bilateral partner qualification with Lexware team

"For deeper integration scenarios, such as financial accounts or transaction processing, Lexware provides a Partner API. This version requires a bilateral partner qualification with the Lexware team, after which you receive OAuth 2.0 credentials with specific scopes." — Maesn Blog

Confidence: High for mechanism; Unknown for exact scope list and what's available beyond Public API.

Via Maesn

Maesn handles authentication to lexoffice on behalf of the integration. Orcha authenticates to Maesn; Maesn authenticates to lexoffice using stored credentials. The customer connects their lexoffice account through Maesn's drop-in frontend components.

Confidence: High

4. Invoice/Document Submission

This is the most critical section for Orcha's use case. Orcha needs to submit structured AP invoice data to lexoffice.

Path A: Native Voucher Creation (BLOCKED for AP)

The vouchers endpoint (POST /v1/vouchers) supports creating vouchers with structured line items, posting categories, contacts, and tax information.

However, creation is restricted to sales voucher types:

"Create vouchers (restricted to sales vouchers)" — Microsoft Learn Connector

"Auf Ausgabenbelege kann per Public API nur lesend zugegriffen werden." (Expense vouchers can only be read via the Public API.) — Lexware Bookkeeping Cookbook

The forum discussion confirms user demand:

"Zum Erstellen gibt es aber keinen Endpoint?" (There is no endpoint for creation?) — lex-forum.net

Synesty's integration also confirms:

"Purchase invoices (purchaseinvoice type) are not supported by this integration. The integration is specifically designed for sales-related vouchers, not procurement documents." — Synesty Docs

Writable voucher types: salesinvoice, salescreditnote Read-only voucher types: purchaseinvoice, purchasecreditnote

Confidence: High — Multiple independent sources confirm this restriction.

IMPORTANT NOTE: The search result snippets about the voucher endpoint listing purchaseinvoice as a voucher type refer to filtering/reading vouchers, NOT creating them. This distinction is critical and is a source of potential confusion in the search results.

Path B: File Upload to Receipt Inbox

The POST /v1/files endpoint with type=voucher uploads a document (PDF, image) to the lexoffice receipt capture inbox ("Belegerfassung").

POST https://api.lexware.io/v1/files
Content-Type: multipart/form-data
Authorization: Bearer {accessToken}

file=@invoice.pdf
type=voucher

After upload:

• The file appears in lexoffice's "receipt capture" area
• Lexoffice applies its own OCR to extract data
• The document lands in a "To Review" state
• A human (or lexoffice's own automation) must then process it into a voucher

"Once you open the receipt, OCR text recognition automatically reads the relevant receipt data and enters it directly." — Lexware Belegerfassung

Implications for Orcha:

• Orcha's structured data (extracted line items, GL accounts, amounts) cannot be transmitted through this path — only the PDF file
• Lexoffice will re-do its own OCR, potentially with different results
• The document requires human review in the lexoffice UI
• This path works as "document delivery" but not "structured data submission"

Confidence: High for the mechanism; Medium for exact post-upload behavior (needs testing).

Path C: Upload File to Existing Voucher

POST /v1/vouchers/{id}/files attaches a file to an already-existing voucher. This requires the voucher to exist first — and since purchase invoices can't be created via API, this path only works if:

1. The voucher was created manually in lexoffice first, OR
2. The file upload (Path B) triggers voucher creation, and you can then update it

Confidence: Medium

Path D: Email Forwarding

"You create a custom address like ihrefirma@inbox.lexware.email" — Lexware Help Center

Limitations:

• Max 5MB per file
• Max 10 files per email
• Only attachments processed (not email body)
• Requires Lexware Office XL subscription
• Files land in "To Review" — same as Path B

This is essentially the same as Path B but via email instead of API. Not suitable for automated structured data transfer.

Confidence: High

Path E: Maesn Bills Endpoint (Most Promising)

Maesn's unified API includes a bills endpoint with create, retrieve, update, and delete operations. Bills in accounting terminology typically represent incoming invoices / accounts payable — exactly what Orcha needs.

"Maesn normalizes data across a multitude of ERP and Accounting systems into a unified schema." — Maesn

Maesn describes the lexoffice workflow:

"Creating financial transactions involves multiple steps: first creating the transaction which returns an internal ID and external reference, then updating or finalizing the associated financial account, uploading attachments, and finally linking them to the transaction using the external reference." — Maesn Blog

How Maesn might handle this:

1. Use the file upload endpoint to place the PDF in lexoffice
2. Use Partner API access (as a Lexware Technology Partner) to create/update the voucher
3. Combine multiple API calls into one unified operation
4. Use passthrough to access endpoints not exposed in the unified API

This is the highest-priority path to verify. If Maesn can create bills in lexoffice, it solves the core integration challenge and leverages Orcha's existing Maesn relationship.

Confidence: Medium — Maesn lists bills as an endpoint and lexoffice as a supported system, but whether bill creation works for lexoffice (given the underlying restriction) is unverified.

Summary of Submission Paths

5. Master Data Access

Contacts (Suppliers)

Full CRUD via GET/POST/PUT /v1/contacts.

"The lexoffice API allows you to create, retrieve, and update contact information for customers, suppliers, etc. You can specify roles as a list (for example: ['customer', 'vendor'])" — Rollout

• Filter by vendor=true to get suppliers
• Filter by name, email, number
• Supports pagination
• Contacts include: addresses, email, phone, tax number, VAT ID
• Contact persons supported (max 1 per contact via API)
• Collective contacts ("Sammel-Kunde", "Sammel-Lieferant") available for one-time counterparties

Limitations:

• Max 1 billing + 1 shipping address per contact (API limit)
• Max 1 email per type per contact (API limit)
• Max 1 phone per type per contact (API limit)
• Max 1 contact person per contact (API limit)

Confidence: High

Posting Categories (Chart of Accounts equivalent)

"This endpoint provides read access to the list of posting categories for the (bookkeeping) vouchers revenue or expense which are supported in lexoffice." — Microsoft Learn Connector

GET /v1/posting-categories returns a fixed set of categories with UUIDs. These are NOT a traditional chart of accounts with individual GL account numbers. They are high-level categories that lexoffice uses internally for bookkeeping.

Known categories from the bookkeeping cookbook:

Special categories (no collective contacts): Construction Services section 13b, Intra-EU Supply, Third-country Services, Third-country Exports, Small Business Exemption Income.

Orcha implication: There is no traditional "chart of accounts" to import. Posting categories are a fixed, small set. Orcha's GL account assignment would need to map to these categories rather than specific account numbers.

Confidence: High

Cost Centers

No cost center endpoint exists in either the Public API or Partner API documentation. Lexoffice does not appear to support cost centers as a concept in its data model.

Confidence: High (that no endpoint exists)

Articles (Products/Services)

Full CRUD via /v1/articles. Can be used in line items of sales vouchers. Filter by article number, GTIN, type.

Confidence: High

Via Maesn

Maesn's unified API provides:

• accounts endpoint (chart of accounts) — create, retrieve
• suppliers endpoint — create, retrieve, patch
• customers endpoint — create, retrieve, patch
• dimensions endpoint — could potentially map to cost centers
• tax-rates endpoint — retrieve

Whether these all work for lexoffice specifically needs verification. The chart of accounts endpoint in Maesn may abstract over lexoffice's posting categories.

Confidence: Medium

6. Historical Bookings / Journal Entries

Native API

There is no journal entries endpoint in the native lexoffice API (Public or Partner).

Partial alternative: The voucherlist endpoint (GET /v1/voucherlist) provides a list of all vouchers with metadata. This includes:

• Voucher type, number, date, status
• Contact information
• Total amounts
• Created/updated timestamps
• Can filter by type, status, date range

"Get voucherlist (bookkeeping) vouchers (e.g. salesinvoices, salescreditnotes), invoices (including down payment invoices), credit notes, order confirmations, quotations, and delivery notes." — Microsoft Learn Connector

The Partner API's Finance endpoint provides financial accounts and transactions data, and the ability to "Retrieve Assigned Vouchers for a Financial Transaction." This could provide bank transaction/payment matching data.

Confidence: High (for voucherlist); Medium (for Partner API Finance endpoint details)

Via Maesn

Maesn's unified API offers:

• journal-entries endpoint (create, retrieve, bulk create, attachments)
• journals endpoint (retrieve)
• trial-balance endpoint
• transactions endpoint
• open-items endpoint

Whether journal entry retrieval works for lexoffice (where no native endpoint exists) is unclear. Maesn may synthesize journal data from vouchers, or this endpoint may simply not be available for lexoffice connections.

Confidence: Low — The endpoint exists in Maesn's schema, but whether it returns data for lexoffice is unverified.

7. Status & Feedback

Webhooks (Event Subscriptions)

"Using event subscriptions you will be notified about certain events on resources — e.g. you receive a notification every time a contact changes in lexoffice." — Lexware API Docs

Endpoint: POST /v1/event-subscriptions

Confirmed event types:

• invoice.status.changed — when invoice status changes
• contact.changed — when a contact changes
• payment.changed — referenced in examples
• token.revoked — when API connection is terminated or API key is deleted

"Lexware unterstützt neben Events fur Rechnungen auch Events fur Kontakte" (Lexware supports events for contacts in addition to invoices) — Lexware Public API Cookbook

The full list of event types was not extractable from search results. The pattern is {resource}.{event} in lowercase.

Webhook requirements:

• Callback URL must have valid HTTPS certificate (Grade A or better)
• Successful delivery: HTTP 200, 201, 202, or 204
• Retry strategy: Phase 1 — 5 retries at 10, 20, 40, 80, 160 seconds; Phase 2 — 20 retries every 2 hours after a 30-minute pause
• HMAC signature verification via X-Lexware-Signature header

Webhook payload includes: organizationId, eventType, resourceId, eventDate.

Confidence: High for mechanism; Medium for complete event type list.

Voucher Status Flow

Vouchers have statuses: draft, open, paidoff, voided (all read-only via API — status transitions happen within lexoffice).

Confidence: High

Payment Information

GET /v1/payments/{id} — read-only access to payment status of vouchers including invoices and credit notes.

Confidence: High

Deeplinks

Lexoffice provides deeplinks to view/edit resources in the web UI:

• {appbaseurl}/permalink/vouchers/view/{id}
• {appbaseurl}/permalink/invoices/edit/{id}
• etc.

Useful for linking Orcha users directly to the document in lexoffice.

Confidence: High

Unresolved Questions

Suggested Hands-On Testing Plan

Prerequisites

1. Create a free Lexware Office trial (XL features for 30 days)
2. Generate a Public API key with all permissions
3. Set up a Maesn test account (free tier, 30 days)

Test Sequence

Phase 1: Native API Exploration (1-2 hours)

1. GET /v1/posting-categories — document the complete response (all categories, UUIDs, types)
2. GET /v1/contacts?vendor=true — verify supplier listing
3. POST /v1/contacts — create a test supplier
4. POST /v1/files with type=voucher and a sample invoice PDF:
   • Record the response (file ID, any metadata)
   • Check the lexoffice UI: where does the file appear?
   • Does OCR run automatically? How long until data is pre-filled?
   • Can the resulting voucher be retrieved via GET /v1/vouchers?
5. Attempt POST /v1/vouchers with voucherType=purchaseinvoice — confirm the expected 4xx error and document the error message
6. POST /v1/vouchers with voucherType=salesinvoice — confirm sales vouchers work
7. POST /v1/event-subscriptions with various eventType values — discover which are accepted
8. GET /v1/voucherlist — examine the response structure for historical data

Phase 2: Maesn Integration (1-2 hours)

1. Connect lexoffice account to Maesn
2. GET /accounting/suppliers — verify supplier data flows through
3. POST /accounting/bills — attempt to create a purchase invoice, record response
4. GET /accounting/accounts — check what chart of accounts data is available
5. GET /accounting/journal-entries — check if journal data is available for lexoffice
6. Test passthrough: POST /accounting/passThrough with path files, method POST

Phase 3: Webhook Verification (30 min)

1. Set up a webhook receiver (e.g., webhook.site)
2. Create event subscriptions for all discovered event types
3. Trigger events (create invoice, update contact, upload file)
4. Document payload structure and timing

Dead Ends

1. Celigo — No lexoffice connector exists; universal connector is too generic to add value
2. Direct purchase invoice creation via native API — Explicitly blocked; expense vouchers are read-only
3. Synesty lexoffice-CreateVouchers — Limited to salesinvoice and salescreditnote; confirmed purchaseinvoice is not supported
4. OpenAPI spec on GitHub — The gist URL returned 404; no public OpenAPI/Swagger spec found
5. Email forwarding as structured data submission — Only delivers file attachments, no structured data; requires human review
6. lexoffice-voucher-upload GitHub project — Deprecated; authors note lexoffice now supports direct email forwarding

Sources

Official Documentation

• Lexware Public API Docs — Primary API reference (note: JavaScript-heavy, some sections don't extract well)
• Lexware Partner API Docs — Partner-specific endpoints and OAuth 2.1
• Lexware Bookkeeping Cookbook — Critical source for voucher type restrictions
• Lexware Public API Cookbook — Webhook setup guide
• Lexware Help: Email Receipt Upload — Email inbox feature docs
• Lexware Belegerfassung — Receipt capture feature description
• Lexware Pricing — Subscription tiers and pricing

Intermediary / Middleware Documentation

• Maesn: What is Maesn — Unified API overview
• Maesn: Lexware Office API Blog — Detailed lexoffice integration description
• Maesn: Passthrough Docs — Direct API access through Maesn
• Maesn: Integrations — Supported systems list
• Maesn: llms.txt — Complete endpoint inventory
• Chift: Lexware Office — Chift integration page
• Chift: Unified Accounting API — Accounting API overview

Community & Third-Party

• lex-forum.net: purchaseinvoice erstellen — Forum discussion confirming no purchase invoice creation endpoint
• Microsoft Learn: Lexoffice Connector — Power Platform connector (confirms sales-only voucher creation)
• Make.com: Lexware Office — Make.com connector actions
• Synesty: lexoffice-CreateVouchers — Confirms sales-only voucher types
• Rollout: lexoffice API Guide — API overview and OAuth2 guide
• Sysix/lexoffice-php-api — PHP client library
• Maki-IT/lexoffice-voucher-upload — Deprecated upload tool (notable for deprecation reason)
• Rechnungsradar — Third-party receipt capture tools for lexoffice

Retractions

1. Earlier search result summaries suggested purchaseinvoice could be created via POST /v1/vouchers. This is incorrect. Multiple authoritative sources confirm voucher creation is restricted to sales types. The confusion arose because purchaseinvoice is a valid filter value for listing vouchers, not for creating them.

2. One search result summary stated Maesn "confirms bill creation for lexoffice." This is an overstatement. Maesn lists bills as a unified API endpoint and lexoffice as a supported system, but no source explicitly confirms that bill creation works specifically for lexoffice connections. The generic description of multi-step workflows is not the same as confirmation.