> For the complete documentation index, see [llms.txt](https://docs.solutioo.de/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.solutioo.de/differenzbesteuerung/differenzbesteuerung_en_us/overview.md).

# Margin tax: your user guide

**solutioo Margin Tax** extends Microsoft Dynamics 365 Business Central with individual and aggregate margin taxation under [section 25a of the German VAT Act](https://www.gesetze-im-internet.de/ustg_1980/__25a.html). The app supports purchases and sales of second-hand goods, returns followed by resale, price credits and financial partial credits, and corrections across financial years. It also supports disassembling an eligible item into separately saleable used parts with a documented allocation of the purchase price. Evidence, analysis and adapted invoice and credit memo output make transactions traceable.

Prepared setup templates support **used vehicles and vehicle dismantling, spare parts, electronics, bicycles and e-bikes, machinery, and antiques and collectibles**. See [Setup](/differenzbesteuerung/differenzbesteuerung_en_us/configure/setup.md) for instructions on using the appropriate template.

## What would you like to do?

| Your task                                     | Start here                                                                                         |
| --------------------------------------------- | -------------------------------------------------------------------------------------------------- |
| Check whether the app fits your environment   | [Before you start](/differenzbesteuerung/differenzbesteuerung_en_us/start.md)                      |
| Configure the app for the first time          | [Set up the app](/differenzbesteuerung/differenzbesteuerung_en_us/configure.md)                    |
| Buy and sell one item                         | [Quickstart with screenshots](/differenzbesteuerung/differenzbesteuerung_en_us/work/quickstart.md) |
| Process a return, credit or annual settlement | [Daily work](/differenzbesteuerung/differenzbesteuerung_en_us/work/daily-work.md)                  |
| Resolve an error message                      | [Troubleshooting](/differenzbesteuerung/differenzbesteuerung_en_us/help/troubleshooting.md)        |
| Ask solutioo for help                         | [Support with contact form](/differenzbesteuerung/differenzbesteuerung_en_us/help/support.md)      |

## Finding your way around

The left navigation follows your workflow: **Before you start → Set up the app → Buy and sell → Troubleshooting and support**. Expand a section to see its guides. Use the search above to find field names and error messages.

Numbered markers in each screenshot match the explanation directly below it. The application screenshots show sample data. Accounts and document/item numbers are examples; use your own approved master data. Open an image to enlarge it.

The screenshots show the **German interface**. Steps name the English field and, where useful, its German label so you can find the marked control.

## Three terms to know

* **Acquisition:** evidence of a particular purchase and its tax purchase basis. German action: **Warenzugänge**.
* **Fiscal entry:** the internal record of the sale, margin and included VAT. German action: **Steuerposten**.
* **Invoice output:** the document for your customer. Internal purchase prices, margins and margin VAT must not appear on it.

The technical zero-percent document group represents the gross consideration. The app posts internal margin VAT separately. Eligibility must be reviewed for each acquisition before posting.

For extension developers: [separate developer documentation](https://docs.solutioo.de/differenzbesteuerung-entwicklerdokumentation/differenzbesteuerung_dev_en_us/).


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