Invoice Studio – Invoices, Quotes and E-Invoices with ZUGFeRD and XRechnung (Offline App + Excel)

Invoice software with no subscription: invoices, quotes and e-invoices with ZUGFeRD and XRechnung

App + Excel · 5 languages included (English, German, Bosnian, Serbian, Croatian) · Instant download · One-time purchase, no subscription

Many freelancers write invoices in Word or Excel – and only find out when the client calls back that the date of service is missing, the IBAN has a typo or the small-business VAT note was left off. On top of that comes the e-invoice: in Germany, businesses with more than €800,000 turnover in the previous year must issue e-invoices to other businesses from 1 January 2027, and from 2028 this applies to almost everyone. Exceptions include small businesses under the German small-business rule and small invoices up to €250.

ProPraxisPlan Invoice Studio takes the routine off your hands: you enter the customer and the lines, the app does the maths, checks the required details and creates the e-invoice when you need one.

Buy once. Use offline. No monthly subscription. 14-day money-back guarantee.

What Invoice Studio does for you

• Invoices and quotes in minutes: pick or type the customer, add lines from your item list – totals, tax rates, discounts and deposits are calculated for you.
• Invoice check: shows live what is missing – date of service, tax number, address, IBAN typos, the small-business note (§ 19 UStG in Germany), the customer's VAT ID for reverse charge. “Fix” takes you straight to the field.
• E-invoices in one click: ZUGFeRD PDF and XRechnung (XML) to EN 16931. We checked our files with the Mustang validator.
• Clean numbering: sequential with no gaps. Finalised invoices are locked and corrections go through a credit note, so your invoice sequence stays traceable.
• Payments and reminders: record incoming payments, create a payment reminder or dunning letter as PDF or text.
• Quotes: track their status and turn them into an invoice in one click.
• Make received e-invoices readable: open an XRechnung or ZUGFeRD file, let the app check totals and IBAN, keep the due date in view.
• Overview: outstanding, overdue, paid, a “next up” list and a rough VAT preview for the quarter.
• Professional look: 3 templates, your colour, your logo and a payment QR code (GiroCode) for banking apps.

Who it is for – and who it is not for

A good fit for freelancers, tradespeople, service providers and small companies who want to write invoices simply and correctly – small businesses under the VAT threshold included.

Not a fit if you need full bookkeeping with bank feeds, payroll or a DATEV interface.

In every ProPraxisPlan tool

• Runs on computer, iPhone, iPad and Android – on a phone or tablet you open your app link and add it to your home screen; it then runs like an app, offline too. No installation.
• Excel file with overview and charts, optionally kept in sync automatically in Chrome/Edge
• Secure Sharing by QR code with your team or accountant: you decide the role, password, validity and whether changes need your approval
• 5 languages: English, German, Bosnian, Serbian, Croatian – the invoice itself too
• Dark and light design, sample data to try it out

What you get (instant download, ZIP)

• Invoice Studio as an HTML app in 5 languages
• Excel workbook in 5 languages
• PDF guide in 5 languages (with your app link for phone and tablet)
• Video tutorial (all 5 languages)

Activate and get started

• Activate once: The first time you open the app, enter your name and the activation number from your order email. This needs the internet once, briefly.
• 1 purchase = 1 main device. Your team and more devices join by QR code. New device? Sign out the old one in Settings and activate the new one.
• About once a month the app briefly confirms your licence when you are online. Only the number is checked – your data stays on your device.

On a phone or tablet? Open app.propraxisplan.de/invoice/ and tap “Add to Home Screen”. Then activate it with the activation number from your order email.

Frequently asked questions

Do I need technical skills?
No. You type text and numbers and click buttons. No formulas, no code.

When do I have to issue e-invoices?
For invoices to other businesses in Germany: from 2027 if your turnover in the previous year was over €800,000, from 2028 for almost everyone. Being able to receive e-invoices has been required since 2025. Invoices to private customers are not affected. Status: October 2026 – please check your own case with your accountant.

Does it work outside Germany?
Yes. You set your own currency and tax rates. The e-invoice formats matter mainly for business clients in Germany and other EU countries.

Do I have to issue e-invoices as a small business?
Under the German small-business rule you do not have to issue them, but you must be able to receive them since 2025 – Invoice Studio does both.

Can I bring over my customer list?
Yes, from Excel or CSV. You see which column is which first, and only “Apply” saves.

What if I make a typo?
Drafts can be changed freely. Finalised invoices are corrected with “Correct” (credit note + new invoice). Deleted entries come back with “Undo”.

Where is my data?
Only in your browser on your device. The app reminds you to save a backup regularly.

Where do I find the activation number?
In your order email, under the activation number. Enter it together with your name the first time you open the app – it is your personal key.

Do I need the internet?
Only briefly: once to activate, about once a month for the licence check, and for Secure Sharing. Everything else works offline.

What if I change my computer or phone?
Save a backup in the app, sign out the old device in Settings and activate the new one with the same number. Then load the backup – everything is back.

Do I need Excel?
Not for the app, it runs in your browser. You open the included Excel file with Microsoft Excel or a compatible program.

Can I use the app in my business?
Yes. The licence covers you and your own business, and you add your team by QR code. Only passing it on and reselling are not allowed.

Are there any extra costs?
No. Buy once, no subscription.

Good to know

• 14-day money-back guarantee: If the app is not right for you, write to info@propraxisplan.de within 14 days of purchase and you get the full price back, no long explanation needed. The activation for your order is then switched off. This voluntary guarantee is in addition to your statutory rights.
• Digital product – nothing is shipped. You get the download link right after purchase.
• With Secure Sharing, data is encrypted on your device first.
• Personal licence for you and your business; passing it on and reselling are not allowed.
• Not tax or legal advice. You are responsible for tax rates and exemptions.

Maker: ProPraxisPlan