What is Receipt (Quittung)?
A receipt (Quittung) often only confirms payment. An invoice documents the supply, amounts, and tax with the usual legal fields — critical for input VAT and tidy books.
Small till slips can work as simplified evidence within limits that change over time. For software, hardware, or larger amounts, ask for a full purchase invoice.
General information only — not legal or tax advice. Tax and e-invoice rules can change; the applicable laws control (e.g. § 19 UStG, § 14 UStG). Confirm with a tax advisor or lawyer if unsure.