Invoices in foreign currency and euro conversion

Rechnungskit also creates invoices in foreign currencies (for example USD, CHF, GBP) and additionally converts the VAT into euros. § 14 Abs. 4 UStG does not prescribe a particular invoice currency; for VAT, § 16 Abs. 6 UStG requires conversion into euros.

Which rate is used

• Legally decisive for VAT is the average rate that the Federal Ministry of Finance (BMF) publishes for the month in which the supply is made or a down payment is received (§ 16 Abs. 6 Satz 1 UStG, Abschn. 13.5 Abs. 7 UStAE). This is the default for new projects: "BMF rate of the month of supply".
• The monthly rate is only fixed after the month has ended. For supplies in a past month, Rechnungskit therefore takes the BMF rate directly. If the invoice is created in the same month, this rate does not exist yet. Rechnungskit then calculates provisionally with the ECB daily rate and marks it as provisional on the invoice. How to convert in the VAT return in this case is something to clear up with your tax advisor.
• Two methods only work with permission from your tax office: the ECB daily rate as a fixed method (§ 16 Abs. 6 Satz 3 UStG) and the average rate of the previous month (Abschn. 16.4 Abs. 2 Satz 2 UStAE). The previous month's rate is always known at the time of the invoice.
• Rechnungskit builds the monthly rates from the monthly average of the ECB reference rates, fetches them automatically and rounds to four decimal places. In our comparisons this matched the rate published by the BMF.

Sources: § 16 Abs. 6 UStG, Abschn. 13.5 and 16.4 UStAE

Choosing or switching the method

You find the choice under Settings → DATEV settings, in the section Revenue recognition, under "Foreign-currency conversion (VAT)". If you choose the ECB daily rate or the previous month's rate, you confirm that you have your tax office's permission. Without confirmation, the method saved so far stays active.

Projects created before October 2026 are still on the earlier default, the ECB daily rate. Rechnungskit does not switch them without your doing, but it shows a notice there with a button that switches to the BMF monthly rate. The switch applies to new invoices; invoices already created keep their rate.

The chosen rate is frozen per document and used consistently for the invoice, the e-invoice and the DATEV booking: the euro tax amount shown on the invoice is the same one booked in DATEV.

On the invoice and in reports

On an invoice in a foreign currency, net, VAT and total also appear in euros on the document, stating the rate, the rate month and the source, with the note that no additional tax arises. In the e-invoice according to EN 16931, the euro tax amount is shown in structured form. The rate used is frozen per document, so the conversion stays traceable from the archive and a correction uses the same rate. In the dashboard and in reports, foreign-currency documents are converted with their frozen rate for the euro totals, not counted as the raw foreign-currency amount.

Shopify stores with several currencies

If your Shopify store sells in a currency other than the one your customers see (for example a store in US dollars while the customer pays in Canadian dollars), Rechnungskit issues the invoice in the currency the customers actually paid. That is the consideration for VAT purposes, meaning the value of what you receive from the customers (§ 10 Abs. 1 Satz 2 UStG), not the amount Shopify then pays out to you. For matching and payouts, Rechnungskit keeps using your store's payout currency.

The OSS return has its own statutory rate: the ECB rate of the last day of the reporting period (§ 16 Abs. 6 Satz 4 UStG). Rechnungskit applies this quarterly rate there automatically, independent of the rate of the individual invoice.

Sources: § 10 UStG, § 16 Abs. 6 UStG