The 30/70 calculation
One euro of error becomes 3.33 euros.
A method that infers the whole business from one part of it. In hospitality the audit frequently calculates the beverages alone — the goods input there is manageable and the allocation unambiguous — and transfers the result to the food side through an assumed ratio of roughly 30 to 70. The arithmetic leverage is considerable: overstating beverage turnover by one euro raises total turnover by 3.33 euros. Every error on the narrow side acts on the broad side by a factor of 2.33.
Why the leverage is the real problem
In a full calculation an error acts where it arises. In an inference by ratio it acts everywhere. That does not make the accuracy of the beverage calculation more important than usual — it makes it three times as important. And it moves the dispute: it is not the food side that needs examining, it is the beverage side and the ratio.
The assumptions and how to test them
| Assumption of the method | Where it can break | What shows it |
|---|---|---|
| The 30 to 70 ratio applies to this business | Restaurant, bar, takeaway, catering, delivery — each type has its own ratio | The sales statistics of the business over the period |
| The ratio stays constant across the period | Changes of menu and concept, lunch trade, season, refurbishment | The item master data and the price history |
| Beverage input translates fully into beverage turnover | Beverages used in dishes, staff drinks, breakage, shrinkage, complimentary drinks, vouchers | The operational records kept for this |
| Portion sizes match the standard | House measures, carafes, jugs, happy-hour quantities | The recipes and the pouring practice |
| Food carries a comparable mark-up | Food and beverages carry very different mark-ups | The calculation for each product |
| The takeaway share is negligible | Delivery and collection shift the ratio considerably | The revenue accounts by tax rate |
The more effective route does not run through criticism
The 30/70 calculation is a Verprobung — a plausibility test that infers a result from a few variables. Criticising it means staying inside its logic. Presenting the complete calculation makes it moot: under § 162 Abs. 1 Satz 1 AO estimation applies only in so far as the bases of taxation cannot be established or calculated. What has been calculated does not need to be tested for plausibility. And § 162 Abs. 1 Satz 2 AO requires all material circumstances to be taken into account — a ratio drawn from other businesses does precisely not take the circumstances of this one into account.
What we deliberately do not publish
How we build such a calculation in an individual case is not on this page. The point of attack in a method is public — it follows from the assumptions of the method itself. The calculation with which we replace it is not. Those who need the method will find it in our seminars; those who need the result will find it with us.
What we contribute
We record the complete goods input for the audit period — beverages and food — store the recipe for every product and recalculate the quantity actually produced and sold. That removes the need for a ratio: both sides are calculated, neither is estimated.
The legal provisions cited here are given for information and do not replace legal advice.