ISDOC File

What are ISDOC files and how to open them

Are you having problems opening an ISDOC file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your ISDOC files.

What is an ISDOC file?

An .ISDOC file is an ISDOC Electronic Invoice file.

ISDOC Electronic Invoice (.isdoc) is a Czech national format for fully structured electronic invoices stored in XML. It was developed in 2008 by a working group called "Pracovní skupina pro Elektronické standardy výměny dat" under the association ICT Unie, now maintained by the Czech government agency DIA (Digital and Information Agency). The format lets businesses, public institutions, and individuals exchange invoicing documents so that data can be processed automatically without manual re-entry. It includes line item details, tax breakdowns, supplier and customer identifiers, payment terms, invoice issue dates, and other legally relevant figures.

Software systems that generate invoices - including accounting or ERP software - create ISDOC files using ISDOC schema versions (for example version 6.0.2). The schema defines required and optional document types (such as invoices, credit notes, proforma invoices) and the XML structure for elements like customer party, supplier party, monetary totals, invoice lines, currency, and taxation. The format supports digitally signed documents, using enveloped XML signatures compliant with XML Signature and possibly XAdES, and rules are in place for validating document types, currency consistency, and versioning.

Files with the .isdoc extension are well-formed UTF-8 XML documents following the prescribed ISDOC XML schema. Files begin with the XML prolog and root element Invoice in the ISDOC namespace. Documents can be archived together with attachments under the .isdocx extension or embedded into PDF/A-3 containers as ISDOC.PDF.

Some technical identifier strings frequently found in the content include "INVOICE XMLNS" at the start (indicating the XML namespace), "LEGALMONETARYTOTAL" for monetary sums, "ACCOUNTINGCUSTOMERPARTY" and "ACCOUNTINGSUPPLIERPARTY" for buyer/seller party data, "INVOICELINES" for line-item entries, and "VATCALCULATIONMETHOD" for tax specification; these are part of the XML tags defined in the schema. A .isdoc file typically starts with bytes 0x3C at offset 0 (which is '<', the start of XML markup).

How to open ISDOC files

We have identified one ISDOC opener that is compatible with this specific type of ISDOC file.

Programs that open ISDOC Electronic Invoice files

Last updated: August 7, 2026

Various apps that use files with this extension

These apps are known to open certain types of ISDOC files. Remember, different programs may use ISDOC files for different purposes, so you may need to try out a few of them to be able to open your specific file.

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