A domain transfer is technically a provider/registrar change, in which your domain is moved from a previous service provider (seller/existing account) to a registrar or new host/provider of your choosing. In practice this usually requires what is known as an auth code (authorization/EPP code) and, as a rule, your confirmation/initiation in your new customer portal (with slight variations depending on TLD, registry and security level).
The auth code (also called the EPP/authorization code) is a security feature that ensures only the legitimate domain holder can initiate a transfer. When you start the transfer in your new account, it is usually checked whether your domain is in a transferable state (often: not locked, correctly verified, validly renewed) and whether the code you entered matches the domain.
You can quickly find further terms if needed in the glossary (including ICANN/EPP, registrant, transfer lock).
Many TLDs use asynchronous processes: your new system requests the release, your previous registrar must/can confirm the transfer, registries sit in between, and security factors (emails, confirmation clicks) affect the timings. That is why a hard day-by-day guarantee rarely makes sense when the technical data (TLD, lock, terms, email reachability) is unknown.
The German country-code domain .de is technically governed by DENIC (the registry); however, your practical contract and tooling chain runs through your registrar or their customer portal. For users this means: many processes can be standardised, yet the "final truth" still depends on status, locks, deadlines and possibly additional verifications in your account - not on a single email that one might want to "believe".
If you want to dig deeper into terminology (auth/policy terms, name servers, the data-protection perspective in Whois lookups), use the glossary - and for support cases always keep domain + TLD + registrar to hand, not "some fragment of a contract number".
With many gTLDs there are, in practice, scenarios in which after certain holder/context changes (depending on provider/status) no further registrar transfer is possible for the time being - often intended as a security mechanism. This is not the same as German niche cases and does not apply 1:1 across the board to every TLD.
If you find yourself in this situation, the most correct next step is: read the registrar/customer portal, check the status/history, rather than quickly accepting "RIP domain" in forums.
A common, costly mistake: the domain changes registrar, but DNS stays with the old package, MX points into the void, TLS breaks and monitoring goes off. For business websites the checklist is usually: name server strategy (stay/move), MX (email), SPF/DKIM/DMARC as a reality rather than a buzzword, and DNS TTL set sensibly when a cutover is planned. The transfer is then only one part of the overall system.
The previous provider has to be working in a transferable state (for example: outstanding charges, technical locks, an ongoing transfer conflict). On top of that come user errors, wrong emails and outdated EPP entries.
The target provider has its own security and data-capture procedures. Depending on the TLD/registry, a verification as registrant may additionally be required before the domain goes live.
With a vetted process, the technical focus is on: payment/receipt, handover of the auth code in defined cases, communication, and clear responsibilities at the target registrar. Depending on the TLD, history, status of the domain and any third parties involved, more intermediate steps may be needed than with an "off-the-shelf" domain.
When paying via Stripe checkout, you (and our team, for filing) receive an email with the transaction details immediately after successful payment; the invoice and payment receipt appear, once they are available in Stripe, usually as links in this email or in your documents at Stripe - in practice generally without a fixed PDF email attachment from our end.
If you describe your desired TLD, your preferred target registrar and the current background, expectations and next steps can be assessed much more sharply.
For content around security, see Secure domain trading (basics) and our hub Guides overview. If it is about a specific domain, start in the portfolio list or via the inquiry form - or write to [email protected] with the domain name, TLD, current background and your target registrar (if already known).