Vorsteueraufteilung is the division of input tax when a business has both turnover that carries Umsatzsteuer and turnover that does not. Anything bought for use on both sides has to be apportioned between them somehow.
Umsatzsteuer applies in both directions, because a business charges it on what it sells and reclaims it on what it buys, and the tax it reclaims is the Vorsteuer. That mechanism only works cleanly when every part of the business is taxed.
Where part of the turnover carries Umsatzsteuer and part of it does not, the input tax on anything used for both purposes cannot simply be reclaimed in full, and it cannot simply be dropped either. It has to be divided instead, and that division is the Vorsteueraufteilung.
A pharmacy is already in that mixed position in ordinary trading, and a new service can widen it. A draw offered as an apothekenübliche Dienstleistung, an appointment billed as Privatliquidation, and the medicines on the shelf do not automatically share one treatment.
Two further problems follow from that mixed position:
This is why the timing matters more than the arithmetic. A centrifuge, a measuring device, the fitting out of a consultation room and the consumables that go with them are all bought before there is any turnover to test a treatment against.
The paperwork filed in those first months is what fixes the position, so how the Rechnungsstellung an Selbstzahler is organised and how the purchase invoices are recorded matter from the first day instead of from the first audit. The same structural facts decide the neighbouring Gewerbesteuer question, so both belong in one conversation with the same adviser.
No percentage and no key belongs in a glossary entry, and anyone offering a rule of thumb for this is describing their own client instead of yours. Which turnover is treated how, and which method of division applies to a given house, depends on the mix of services and on the pharmacy's existing treatment, so the question belongs with your Steuerberater before the equipment is ordered.
This glossary entry is general information about German pharmacy law and practice. It is not legal advice. For binding guidance on your own pharmacy, contact your Landesapothekerkammer.