Summary

Who this is for: Intended parents comparing Tammuz’s program options before signing, who want a plain-language explanation of what Single Guarantee, Double Guarantee, Guarantee Plus, and Existing Embryos actually mean before choosing one.

Key takeaways:

• Tammuz’s Guarantee Plans are built around continuing the process, through additional donor eggs, embryo transfers, and surrogate matches, until a live birth, rather than charging separately for each attempt.
• Single Guarantee and Double Guarantee differ in how many intended parents’ cycles run through the program, and the choice between them is locked in early.
• Guarantee Plus follows the same back-to-back cycle structure used in a Double process; your case manager will confirm the specific details that apply to your household during your consultation.
• Existing Embryos is built for intended parents who already have embryos created elsewhere and are shipping them to a Tammuz clinic rather than starting from donor selection.
• Program selection happens at contract signing, and in most cases, it cannot be changed once your first clinic visit has taken place.

What’s inside:

• What “guarantee” actually covers in a Tammuz program
• Single Guarantee vs. Double Guarantee vs. Guarantee Plus, explained
• What Existing Embryos means and who it’s for
• How and when you choose your program
• What happens after you’ve made your choice

Choosing a surrogacy program is one of the first real decisions intended parents make with Tammuz, and it’s also one of the most confusing parts of early research. Single Guarantee. Double Guarantee. Guarantee Plus. Existing Embryos. The names sound similar, and most general surrogacy content online doesn’t explain them in a way that’s specific to how Tammuz actually structures the process.

This is a plain-language walkthrough of what each program means, based on how Tammuz’s case managers describe them internally, and how program selection fits into the early steps of your journey.

What “Guarantee” Actually Means at Tammuz

Across Tammuz’s Guarantee Plans, the underlying idea is the same: the program is built to continue supporting your process, through additional donor eggs, additional embryo transfers, and additional surrogate matches, until a live birth, rather than treating each attempt as a separate, additional charge once you’re enrolled.

In practical terms, that means if a transfer doesn’t result in a pregnancy, or a surrogate match doesn’t work out, the program continues rather than stopping or requiring a new contract. It’s a structure built around reducing the financial uncertainty that comes with a process that, by its nature, doesn’t always go as expected on the first attempt.

This is different from a Pay As You Go or Basic plan structure, where intended parents cover each stage as it happens rather than paying into an all-inclusive program from the start. Guarantee Plans generally aren’t the right fit for everyone; intended parents using the intended mother’s own eggs, or those who arrive with a smaller number of existing embryos, are typically guided toward a different plan structure. Your case manager can walk you through which structure fits your specific situation.

Single Guarantee

A Single Guarantee program is built around one intended parent’s biological process: one source of sperm (or, in some structures, one egg source), moving through donor selection, embryo creation, and transfer as a single track.

For single intended fathers, this is the standard structure. For couples, choosing Single Guarantee means the process moves forward using one partner’s genetic material rather than creating two separate sets of embryos.

Double Guarantee

A Double Guarantee program runs two parallel tracks, one for each intended parent, rather than one. In practice, this means the egg donor is reserved back-to-back for two cycles, one for each intended parent, so that both partners have the chance to have a biological connection to a child through the same journey.

Double Guarantee is not available at every partner clinic. In Mexico, for example, it’s currently offered only through specific clinics, and a gap between the two processes isn’t possible; the two tracks run in parallel rather than one after the other. Availability and structure can vary by destination, which is exactly the kind of detail your case manager will confirm once you’ve chosen where you’re pursuing your program.

One detail worth knowing early: if you sign as a Single Guarantee and later want to move to Double Guarantee, that change is generally only possible before your first visit to the clinic. Once that first visit has taken place, the program selection is considered final, including for single intended parents who later wish to add a second track.

Guarantee Plus

Guarantee Plus is offered as a distinct program selection alongside Single Guarantee and Double Guarantee, and it follows the same back-to-back cycle logic used for Double processes, meaning the donor is reserved for two cycles rather than one. Because the exact way Guarantee Plus is structured can vary by destination and by household, this is a program where it’s worth asking your case manager directly, during your consultation, how it applies to your specific circumstances before you sign. We’d rather you get a precise answer from your case manager than a general one from a blog post.

Existing Embryos

The Existing Embryos plan is built for intended parents who already have embryos created at another clinic and are shipping them to a Tammuz partner clinic rather than starting the process with donor selection.

This changes the shape of the early timeline. Instead of waiting on donor availability, your wait for a surrogate profile generally begins once your embryos (and, depending on destination, your documentation and payment) have arrived at the clinic. In Mexico, for instance, Existing Embryos intended parents don’t wait through the standard waitlist period tied to signing a new contract; the clock starts once the embryos land. In the USA, Existing Embryos intended parents generally need at least three embryos to qualify for the Guarantee Plan structure; with fewer than three, the Pay As You Go plan is used instead.

Before your embryos ship anywhere, the receiving clinic will need to review and approve the shipment. Exactly what that approval involves, from infectious disease testing on the original egg and sperm sources to specific medical forms and consents, depends on the destination and clinic you’re shipping to. Your case manager will walk you through exactly what your specific clinic requires.

How and When You Choose Your Program

Program selection happens at the same time you sign your Tammuz contract. You’ll indicate which program you’re enrolling in directly on the contract, alongside your Tammuz IP Information, which needs to be typed rather than handwritten.

This is also the point to ask questions. Because switching between programs, particularly moving from Single to Double Guarantee, is only possible before your first clinic visit, it’s worth taking the time here rather than assuming you can adjust course later. Your case manager is there to walk through the tradeoffs with you before anything is finalized.

What Happens After You Choose

Once your program is selected and your contract is signed, the shape of your journey follows a fairly consistent sequence, regardless of which Guarantee Plan you’ve chosen: document submission and screening, your first visit to the clinic, donor selection (unless you’re on an Existing Embryos plan), surrogate matching once embryos are ready for transfer, embryo transfer itself, pregnancy monitoring through to delivery, and the legal process that follows birth.

The specifics of that sequence, timelines, required documents, and what each stage looks like, vary by destination. If you’re also weighing where to pursue your program, our comparison of the USA, Mexico, and Colombia walks through how the process differs by country.

Ready to figure out which program fits your family?

Every household’s situation is different, and the right program depends on factors like your genetic material, your embryo status, and your destination. A free consultation with the Tammuz team is the most direct way to get a straight answer about which Guarantee Plan makes sense for you.

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Frequently Asked Questions About Tammuz Guarantee Plans

What does a “Guarantee Plan” actually guarantee?

A Guarantee Plan is structured so that the program continues, through additional donor eggs, embryo transfers, and surrogate matches, until a live birth, rather than charging separately for each new attempt. The specific inclusions and any program limits are confirmed in your contract and by your case manager.

What’s the difference between Single Guarantee and Double Guarantee?

Single Guarantee runs one intended parent’s process as a single track. Double Guarantee runs two parallel tracks, one for each intended parent, with the donor reserved back-to-back for both cycles.

Is Double Guarantee available everywhere?

Availability varies by destination and by clinic. In Mexico, for example, Double Guarantee is currently offered only through specific partner clinics. Confirm availability for your chosen destination with your case manager.

Can I switch from Single Guarantee to Double Guarantee after I sign?

In most cases, yes, but only before your first visit to the clinic. Once that visit has taken place, the program selection is generally considered final, including for single intended parents who later want to add a second track.

How is Guarantee Plus different from Double Guarantee?

Both follow a similar back-to-back cycle structure. Because the specific differences can vary by destination and household, we recommend confirming the exact details of Guarantee Plus with your case manager during your consultation rather than assuming a one-size-fits-all definition.

What is the Existing Embryos plan for?

It’s built for intended parents who already have embryos created at another clinic and are shipping them to a Tammuz partner clinic, rather than starting with donor selection. Your timeline generally begins once your embryos (and required documentation) arrive at the clinic.

Do I need a minimum number of existing embryos to qualify for a Guarantee Plan?

It depends on destination. In the USA, for example, intended parents generally need at least three existing embryos to qualify for the Guarantee Plan; with fewer, the Pay As You Go plan applies instead. Ask your case manager about the requirements for your specific destination.

When do I choose my program?

Program selection happens when you sign your Tammuz contract, at the same time you provide your Tammuz IP Information.

Does choosing a Guarantee Plan affect which destination I can use?

Program availability, including which Guarantee options exist and at which clinics, varies by destination. It’s worth discussing both your program and destination preferences together with your case manager rather than deciding one in isolation.

Who should I talk to if I’m not sure which plan fits my situation?

Your case manager is the right first stop, and a free consultation with the Tammuz team is a good way to get specific answers before you sign anything.