Tax audits and the investment deduction amount: what the tax office actually checks

An investment deduction amount shifts tax into the future, and anything that shifts tax eventually gets looked at to see whether it was justified. For investors who, through a direct investment, hold their own commercial business for the first time, this is unfamiliar ground: with a salary, interest income or a rented flat, nobody ever comes by. This article describes the procedure as it actually works: who may be audited, how likely that is, which §7g points really are on the auditor's list, which documents have to be ready for them, and what the modernisation of the German field audit changed from 2025.

Who can be audited at all?

Anyone who operates a commercial business, and that includes every direct investment in a solar park or a battery storage system. §193(1) AO simply declares a field audit admissible for taxpayers with a commercial or agricultural business and for members of the liberal professions. No suspicion, no anomaly and no special justification is required; admissibility follows from the existence of the business alone.

For everyone else the threshold is higher. Taxpayers with only non-business income, i.e. salary, investment income or rents, may be audited under §193(2) AO only if additional conditions are met, for instance where a matter requires clarification and an examination at the tax office is not appropriate given its nature and scope; separate record-keeping and retention duties apply to taxpayers with high non-business income under §147a AO. That is exactly where the switch happens: the IAB presupposes a business, and anyone using it moves into the group that may be audited without further justification. This is not a drawback of the direct investment but the flip side of the tax lever itself; the other conditions this business has to meet are set out in Investitionsabzugsbetrag: all §7g EStG requirements, and who can use it.

Does an investment deduction amount automatically trigger an audit?

No. An IAB is not an audit trigger, and the vast majority of small businesses are never field-audited. How cases are selected, however, cannot be reconstructed from the outside: under §88(5) AO the tax offices may use automated risk management systems, and the statute expressly provides that details of those systems must not be published where doing so could jeopardise the uniformity and legality of taxation. All that is prescribed is what every such system must contain, including a random selection through which a sufficient number of cases reaches a comprehensive review by officials. So anyone reading that an IAB leads to an audit “with high probability” is reading a guess, not a figure.

More important than the probability is a distinction that gets blurred constantly in practice. The most common contact with the tax office is not a field audit but a query from the case officer during the ordinary assessment procedure: they want to see the participation agreement, the invoice or proof of commissioning. That is ordinary cooperation in the assessment procedure and has none of the consequences described below. Nor is an assessment issued subject to review under §164 AO an audit: as long as that reservation is in force, the assessment can be amended at any time without anyone visiting. And a provisional note under §165 AO keeps only a single point open, usually the question of profit-making intention.

How does a field audit run?

In five steps, all of them set out in the Abgabenordnung, and their sequence is not at the auditor's discretion:

1. Audit order (§196 AO): the tax authority determines the scope of the audit in an administrative act, i.e. which taxes and which years are covered. Whatever is not listed is not audited; the order itself can be challenged by objection.
2. Notification (§197 AO): the order, the expected start date and the names of the auditors must be notified a reasonable time before the audit begins. The statute sets no fixed number of days; the taxpayer may waive compliance.
3. The audit (§199 AO): the auditor must examine the tax bases both in favour of and against the taxpayer. The taxpayer is to be informed during the audit about the facts established and their possible tax consequences; the statute expressly provides for discussions at regular intervals.
4. Closing meeting (§201 AO): this is the default and is omitted only where the audit results in no change to the tax bases or the taxpayer waives it. Disputed facts and their legal assessment are discussed there; with the taxpayer's consent the meeting may also be held by telephone or electronically.
5. Audit report (§202 AO) and amended assessments: the report records the findings, the assessments implement them. If the audit results in no change, a corresponding notification is sufficient.

In a direct investment the audited business is the investor themselves; there is no separate company that would be audited instead. In practice contact still runs through the tax adviser who holds the bookkeeping. And the scope follows the order: if it says “income tax 2025 to 2027”, the participation is one item among several and rarely the most laborious one.

Which §7g points does the auditor look at?

Essentially five, and all five can be evidenced with documents that arise anyway:

• The profit ceiling. In the financial year of the deduction, profit must not exceed €200,000, calculated without the deduction amounts and the add-backs themselves (§7g(1) sentence 2 no. 1 EStG). What counts is the profit of the business for which the IAB is formed, not your total income.
• The per-business cap. The sum of deductions from the year of deduction and the three preceding financial years, to the extent not yet added back or reversed, must not exceed €200,000 per business (§7g(1) sentence 4 EStG). Where several vintages follow one another, this is the limit you hit first.
• The asset itself. Only depreciable movable fixed assets qualify. Ground-mounted plants and battery storage systems regularly meet this because they are classified as operating equipment rather than part of a building.
• The add-back in the right year. It is made in the financial year of acquisition or production (§7g(2) sentence 1 EStG). The auditor reconciles it against the acquisition date, and that follows from handover and acceptance, not from the date of a down payment.
• The use. The asset must be leased out or used exclusively or almost exclusively for business purposes in a domestic permanent establishment at least until the end of the financial year following acquisition (§7g(1) sentence 1, (4) EStG). For a plant that markets all of its electricity this is unproblematic; it only becomes delicate with significant self-consumption.

A sixth point does not formally belong to §7g but does in practice: profit-making intention. A business that cannot be expected to produce an overall profit across its lifetime is treated as a hobby activity, and all losses including the IAB then fall away. If your assessment carries a provisional note on this point, that is the point that will be revisited later; how the overall-profit forecast is built and why the IAB and special depreciation do not damage it is set out in Liebhaberei and profit intention: when the tax office cancels the tax lever.

Must I prove an intention to invest?

No, and this is one of the most persistent misconceptions on the subject. Under the version in force until 2015, the asset had to be identified “by its function” and the intention to invest had to be set out; anyone audited had to make that intention plausible. None of this remains in current law. §7g(1) EStG ties the deduction to exactly three conditions: profit determination under §4 or §5 EStG, a profit of no more than €200,000 in the year of deduction, and transmission of the amounts by remote data transfer using officially prescribed data sets. Neither a functional description nor proof of intent appears anywhere in it. A source still demanding today that the intention to invest be “concretely demonstrable” is describing a legal position that ceased to apply ten years ago.

In practice that shifts the audit question entirely. The auditor does not ask whether you already intended to invest in the year of deduction. They ask whether you did invest, and if not, whether the deadline running to the end of the third following financial year is still open. For completeness, one qualification belongs here: where a business is only just being established, there is no ongoing operation in the year of deduction, and the tax administration looks more closely at whether a genuine start-up exists. In a direct investment this is not an edge case but the norm, because the business comes into existence with the participation. What has to be shown, however, is nothing soft but something concrete: a signed agreement, a payment schedule, a specific project. The details are governed by the Federal Ministry of Finance's application decree on §7g EStG; classifying your own case belongs with your tax adviser.

Which documents must you be able to produce?

Everything from which the business and the IAB can be traced. §200(1) AO obliges the taxpayer to cooperate in establishing the facts, to provide information and to produce and explain records, books, business papers and other documents. On top of that comes data access: under §147(6) AO the tax authority may, in the course of a field audit, inspect stored data, use the data processing system for the audit or demand a machine-readable evaluation. Retention periods under §147(3) AO are ten years (books, records, annual accounts), eight years (accounting vouchers) and six years (other tax-relevant documents). For a direct investment that means, concretely:

• The signed participation agreement with all annexes, including the technical description of the plant.
• Invoices and proof of payment, including down payments, with their respective dates.
• The acceptance or commissioning protocol establishing the acquisition date.
• The profit determination for the business for every year, including loss years.
• The fixed asset register showing depreciation, special depreciation and the add-back of the IAB.
• Statements from direct marketing or operational management showing the revenues.
• Evidence that the plant is operated in Germany and used entirely for business purposes.

This is the same set of documents needed when changing tax adviser, when arranging bank finance or on a later sale. Keeping it in order from the first year, rather than reconstructing it five years later, already removes most of the audit workload. Which of these records should come out of ongoing reporting is set out in What happens after closing: reporting, asset management and why a partner is not a broker, and where the IAB goes in the return itself is shown in The IAB in your German tax return: where and how to actually claim it.

What changed in 2025 about German field audits?

Three things, and together they move the time pressure from the tax office to the taxpayer. First, under §197(5) AO the audit order should be issued by the end of the calendar year following the calendar year in which the tax assessment took effect; audits are meant to happen closer to the years they cover. Second, the suspension of the assessment period caused by a field audit now ends at the latest five years after the end of the calendar year in which the audit order was notified (§171(4) sentence 3 AO). Until then, an audit once begun could keep the assessment period open almost indefinitely; now there is an outer edge.

Third, and most important in practice, §200a AO introduces the qualified cooperation request. If the taxpayer fails to cooperate, the tax authority can formally demand the documents; the deadline is one month from notification. If it is missed, a delay charge must be imposed: €75 for each full calendar day of delay, for a maximum of 150 calendar days. In the cases named by the statute, an additional surcharge may apply of up to €25,000 for each full calendar day, again for a maximum of 150 days. This is no longer a matter of discretion as under the old delay penalty, but an automatic mechanism with a daily rate.

When this applies is governed by Art. 97 §37 EGAO, and the answer concerns investors directly. Under paragraph 2, the new provisions apply for the first time to taxes arising after 31 December 2024. Paragraph 3 extends them to earlier years where an audit order for those years was notified after 31 December 2024. For an IAB formed for 2025 the new regime therefore applies in full, and so it does for an audit ordered today covering earlier years. Anyone who used an investment deduction amount for the first time in 2025 belongs to the first cohort under the new rules.

The way out is in the statute itself and is rarely mentioned. Under §199(2) AO the tax authority may agree a framework for cooperation under §200 AO with the taxpayer; if the taxpayer keeps to it, no qualified cooperation request under §200a AO is issued. Anyone who records bindingly in the interim discussions what will be delivered by when, and then delivers, removes the provision's field of application. That is the real consequence of the reform: what decides the outcome is not the level of the daily rates but whether communication during the audit is handled properly.

What happens if the auditor strikes the IAB?

The deduction falls away retroactively in the year it was taken, even if the assessment became final long ago. Where the investment was not made in time, §7g(3) EStG orders the reversal and states expressly in sentence 3: “Das gilt auch dann, wenn der Steuer- oder Feststellungsbescheid bestandskräftig geworden ist”, i.e. this applies even where the assessment or determination notice has become final; the assessment period does not end in that respect before the period for the assessment year in which the third financial year following the year of deduction ends. §7g(4) EStG contains the same rule where the use and retention requirement is breached. Finality offers no protection here.

The cost comes through interest. Interest on the back payment accrues under §233a AO at 0.15 percent per month, i.e. 1.8 percent per year (§238(1a) AO). What matters is when the interest period starts: fifteen months after the end of the calendar year in which the tax arose, and §7g(3) sentence 4 and (4) sentence 4 EStG expressly exclude the deferral that would otherwise apply under §233a(2a) AO. An IAB that stood for three years therefore easily carries around two years of interest. What that looks like in figures, and which exits exist before the deadline expires, is worked through in Reversing the IAB: what happens if you don't invest, deadlines, interest, ways out.

One question comes up regularly at this point: can an additional assessment from the audit be cushioned by forming an IAB after the fact? The statute draws a clear line. Under §7g(2) sentence 2 EStG, where deduction amounts are claimed only after the initial assessment has become incontestable, the add-back requires that the qualifying asset had not yet been acquired or produced at that time. An IAB claimed retrospectively for an investment already made therefore comes to nothing. For an investment still ahead, the route may be open; whether it works in the individual case is for your tax adviser to judge on the basis of the assessments.

Checklist: audit-ready from day one

• Keep the agreement, invoice, proof of payment and acceptance protocol in one file per participation vintage, digital and permanently legible.
• Document the acquisition date from the acceptance protocol; do not derive it from the payment date.
• Have the profit ceiling and the €200,000 per-business cap checked before every further IAB vintage.
• Actually make the add-back in the year of acquisition and show it in the fixed asset register.
• Evidence the business use: keep the direct marketing or operational management statements for the year of acquisition and the following year.
• Do not skip loss years: file the profit determination and returns even where no tax arises.
• Observe the retention periods: ten years for books and accounts, eight years for accounting vouchers, six years for other documents.
• On receiving an audit order, read the scope and the years first; questions about them belong before the audit starts, not in the closing meeting.

In our view, audit-readiness is above all a question of the documents a provider supplies unprompted: whoever delivers the acceptance protocol, the invoicing and the ongoing statements cleanly spares their investors exactly the reconstruction work described here years later. In a non-binding initial consultation we are happy to show which records we hold for a specific project and what the reporting looks like afterwards, in coordination with your tax adviser.