Nearly everyone in this market reads English comfortably, which sounds like a simplification and is actually a trap. Because the audience can read an English page, businesses convince themselves they can run one site in one language and be done. Then they look at where the enquiries come from and discover that when people are ready to buy, they search in their own language, and the results they get are filled with competitors who write in it.
Buyers in the Netherlands search in two languages, often for the same thing
The pattern is consistent and it is worth understanding before you brief anyone. Technical and professional vocabulary is frequently English, because that is the working language of the industry. Commercial intent tends to revert to Dutch, because that is the language of deciding and paying. The same person will research a product in one language and look for a supplier in the other.
So the useful question for a prospective SEO supplier is not which language the site should be in. It is which phrases belong in which language, and what evidence they have for the split. A firm that has genuinely worked here will describe the mixture. A firm that has not will recommend translating everything, which is both expensive and wrong.
English only content quietly loses the phrases that SEO is bought for
The symptom is a site with healthy visibility, decent visitor numbers, and almost no enquiries from the domestic market. Everything looks fine in the report because the English pages pick up international and informational traffic. Meanwhile the phrases that produce orders are held by Dutch language competitors, and nobody notices because those phrases were never on the tracked list.
Ask any SEO agency to show you, for two or three of your core products, what the demand looks like in each language side by side. It takes very little time and it settles the argument with data rather than opinion. If the answer is that domestic demand is small, fine, you have learned something useful. If the answer is that it is substantial and unserved, you have found the work.
A small supplier pool rewards a precise brief
The number of agencies here that do this properly is not large, and the good ones are frequently busy. That changes your negotiating position in a specific way: vague requirements get deprioritised, and precise ones get taken seriously. Arrive at an SEO conversation with your target phrases, your markets, your languages and your commercial numbers written down, and you will be a better client to win than a larger business that has not done the thinking.
It also means a wider search is reasonable. Nothing about this work requires proximity, and suppliers elsewhere can be excellent provided they have a native speaker doing the language that matters. What they cannot do remotely is understand your market, so weight sector experience above location.
Online retail decisions belong to merchandising, not to the agency
This is one of the most developed markets anywhere for buying online, and a large share of the sites being optimised here are shops. That changes the shape of an SEO engagement in ways proposals rarely acknowledge. The important decisions are about category structure, filters, how variants are handled, what happens to a product that goes out of stock, and whether the feed and the site agree with each other.
All of those are commercial decisions with a search consequence, which means the agency cannot make them alone and should not be asked to. Establish before any SEO work starts who owns the taxonomy and who is allowed to change a page address, because in a shop a careless restructure destroys more value in an afternoon than a content programme creates in a year.
Fee models and what the monthly number actually covers
Ask for the fee to be split into three lines: analysis and strategy, production, and running the programme. The split does more work than any other request, because it exposes the attractive monthly figure that excludes all writing, and the expensive one that is mostly account management on top of subcontracted delivery.
If Dutch language production is in scope, ask for it to be costed as its own line with a named writer behind it. That is the single fastest way to tell a real bilingual capability from a claim. If gathering comparable answers from several firms is the part you would rather avoid, set out the requirement once and ask for replies in a fixed shape.
Accounts, feeds and the material you keep
Analytics and console properties, the tag container, the content system, the product feed configuration and the domain registration belong in accounts owned by your business, with the agency granted access. Written material transfers on payment with source files.
Two things particular to this kind of work are worth naming explicitly. The bilingual phrase list, which records what your buyers type in each language and is the most valuable by-product of a year of SEO work. And the redirect map, because a shop restructure without one is how businesses lose years of accumulated position in a single release.
Set the commercial measure at the same time: one number stated in your terms, with visibility data kept underneath as a diagnostic, and every comparison made against the same period a year earlier. For the wider picture of how these suppliers are organised, start from the overview of SEO agencies. If the work is as much about the shop as the search, look at firms that specialise in online retail, and if you want to compare supplier markets nearby, weigh your shortlist against agencies in the largest domestic market or firms just over the southern border, or talk to teams running paid social nationally.