GAEB file explained: X81, X83, X84, X86 and what is inside

A GAEB file is a bill of quantities (BoQ, in German Leistungsverzeichnis or LV) in structured form. Every item, quantity, price and text sits in a fixed place that a program can read. The exchange phase, such as X81, X83, X84 or X86, says where in the procurement sequence the file belongs and who produced it in which role. This matters for checks, because a fixed program can then calculate and compare, while the AI reads only the texts.

What is inside a GAEB file

GAEB stands for Gemeinsamer Ausschuss Elektronik im Bauwesen, the joint committee for electronics in construction. Its office is based at the Federal Office for Building and Regional Planning (BBR) in Bonn, and it publishes the rules for data exchange. The current format is called GAEB DA XML. It describes the exchange in XML, a markup language for complex structures, and the technical documentation of the GAEB lays it down. As of November 2026 the GAEB website names version 3.3, edition 2023-01, as current. In this edition only the quantity-take-off package (X31) was revised; the other packages, including the one for the bill of quantities with X81 to X87, remain at the 2021-05 edition. A version 3.4 (edition 2026-03, for sustainability data such as life-cycle assessment) exists only as a beta for testing. Whether it will one day replace 3.3 is open.

The file holds the bill of quantities as a structure ordered by item numbers, with descriptions of the individual works. Each item has a quantity, a unit and, depending on the phase, prices. There is a long text that describes the work and an optional short text. According to the technical documentation, only the long-text BoQ applies to carrying out the work, while the short text serves as a quick reference.

A GAEB file is therefore not a picture of a page. It contains the components of the bill, separated and named.

The exchange phases

The GAEB assigns files to phases that follow the course of a procurement. The code begins with X and a number. Four matter in everyday cost and BoQ work:

Phase	Name according to GAEB	What is in it
X81	Leistungsbeschreibung (description of works)	Building description, BoQ and annexes; the BoQ as a rule contains no prices
X83	Angebotsaufforderung (invitation to tender)	The BoQ without prices goes to interested firms with the invitation to submit a tender
X84	Angebotsabgabe (submission of tender)	The BoQ with the bidder’s prices, text additions and free quantities
X86	Auftragserteilung (contract award)	The order to the bidder with the most economic tender

The GAEB website lists further phases. X82 is the cost estimate with estimated prices, X85 the alternative tender, X87 the order confirmation and X89B the supporting document for an invoice, which according to the technical documentation is not an invoice in the sense of German commercial law. For time-based contract work there are separate variants such as X83Z, X84Z, X86ZR and X86ZE.

1. X81 Description Building description, BoQ (mostly no prices), annexes
2. X83 Invitation BoQ without prices goes to interested firms
3. X84 Tender Bidders add prices, texts, free quantities
4. Evaluation Price comparison: program calculates, AI reads texts AI prepares
5. X86 Award Contract awarded after evaluating the tenders

Text version of the graphic

• 1. X81 Description: Building description, BoQ (mostly no prices), annexes
• 2. X83 Invitation: BoQ without prices goes to interested firms
• 3. X84 Tender: Bidders add prices, texts, free quantities
• 4. Evaluation: Price comparison: program calculates, AI reads texts (the AI prepares)
• 5. X86 Award: Contract awarded after evaluating the tenders

Two rules from the technical documentation make the connection tangible. With the invitation to tender (X83) a unique key is set, which the bidder returns unchanged with the tender (X84), so that tender documents and tender match clearly. And in the tender, the information on the project, the bill and in particular its structure is to be taken over unchanged from the invitation. The bidder enters prices and additions, and does not rebuild the bill.

The GAEB describes the evaluation of the tenders received as a price comparison, at the level of unit rates and across the tender total. The technical documentation lists the price comparison as a phase of its own (X84P), but only in beta status.

The difference from PDF and Excel

A PDF is made for reading on screen and on paper. A program that is meant to extract items and prices from it must first recognise the page as text and table, and with scans also needs text recognition. Column assignments and characters get lost on the way, as the article on old plans and poor scans shows for drawings. An Excel sheet can be read by machine, but every sheet is built differently. Columns have different names, rows are merged, and texts sit in comments. A program has to guess the structure first.

A GAEB file has a fixed, documented structure. Item number, quantity, unit, unit rate and long text each have their place. That is no guarantee of error-free content. Mistakes in the bill itself remain mistakes, but they are easier to find.

Why this matters for checks

Checking bills of quantities and tenders consists of two kinds of work.

The first is calculating and comparing: quantity times unit rate, totals, deviations between two tenders or between a tender and the invitation, items that are missing or appear twice. A fixed program does this reliably, because it takes the figures from fields and does not interpret them from a text. A language model produces probable text and is not built for arithmetic.

The second is reading. Has the bidder changed the item text? Does a text addition contain a reservation? Does a preamble contradict an item? Here the language model helps. It reads many texts quickly and marks passages that a person should look at. It does not judge whether a change is permissible or whether an item is priced appropriately.

The structured file makes it possible to keep this separation clean. The number fields go to the program, the text fields to the AI, and both results end up in one list that you check. With a PDF the AI would have to extract both from one page, and the figures would be the weakest point.

What the AI does not do here

It does not decide whether a price is appropriate or a tender should be accepted. It does not replace a review of the description of works by specialists, and a GAEB file does not improve a badly written bill. How to check a bill for errors is a separate topic and not covered here.

Which phase your programs produce or expect depends on your software and your partners. Procurement law questions, for example whether a procedure requires electronic tenders, are for your legal adviser or the contracting authority to clarify in the individual case.

Prices and tenders are confidential business data. They belong only on a platform that can be operated in line with the GDPR, not in a consumer chat service. Your data protection officer clarifies that.

What you can do now

1. Look in your estimating or tendering software to see which GAEB version and which phases it exports and imports.
2. At your next tender, ask for tenders as a GAEB file (X84) as well as PDF, where the procedure allows it.
3. File the GAEB files of a project named by phase, so that X83 and the matching X84 files can be found together. The article on searchable project files shows what a searchable filing system looks like.
4. For a completed project, check which evaluations you rebuilt by hand in spreadsheets and which of them a program could read directly from the file.