The honest answer: it depends on your starting point
E-max veneers are often described as "minimal prep," and for good reason — the material is strong enough to work well even at a fraction of a millimetre thick, which means far less tooth needs to be removed than with older veneer materials or a full crown. But "minimal" isn't the same as "none" for every case.
When very little or no reduction is needed
If your teeth are already reasonably well-aligned and you mainly want to change colour, close small gaps, or refine shape slightly, a thin E-max veneer can often be bonded with little to no removal of enamel — sometimes called a "no-prep" or "additive" approach.
When more preparation is genuinely necessary
If a tooth is significantly out of alignment, has an uneven or bulky shape, or is heavily discoloured in a way that would show through a very thin veneer, some enamel reduction is usually needed so the veneer can sit naturally rather than looking overbuilt. This is a normal, standard part of veneer dentistry — not a sign that something has gone wrong with the plan.
Why this should be decided before you travel, not after
A digital smile design scan, done before any preparation, is what actually answers this question for your specific teeth — not a general rule. It lets your dentist show you what's achievable with minimal preparation versus what would need more, so you know what to expect before treatment starts.
What to ask
It's entirely reasonable to ask directly: "how much of my natural tooth will you need to remove for this design?" A clinic that has actually planned your case digitally should be able to answer specifically, not with a generic "don't worry, it's minimal."