Moving marketplace advertising to a new service partner sounds like a sensible operational project. Export the Amazon campaigns, invite the new agency, share the bol.com login, explain the MediaMarkt retail media budget, schedule a kickoff and keep the ads live. Very tidy. Also exactly how a profitable account gets accidentally reset.
The named mistake I see with brands spending from roughly €5K per month is treating migration as an access handover instead of a profit cutover. The new operator receives campaigns, but not the commercial memory behind them. They see bids, but not why a SKU was capped at 18% ACOS. They see negative keywords, but not which terms were blocked because stock was thin for two weeks. They see a monthly budget, but not which hours, marketplaces and product families were allowed to spend it.
My stance: a marketplace ad service migration should not start with optimisation. It should start with a cutover ledger: a short, brutally practical document that tells the incoming operator which products are allowed to scale, which campaigns are under probation, which rules are frozen, and which data must not be trusted yet.
This guide is for ecommerce brands in the Netherlands and Belgium moving Amazon, bol.com or MediaMarkt ad management to a specialist marketplace advertising service. The goal is not to copy every old setting. The goal is to preserve the decisions that still protect profit while giving the new team enough room to improve the account.
What migration advice gets right
The research landscape around migration is useful, even when most of it comes from website hosting rather than advertising. WP Engine’s migration material focuses on protecting uptime, SEO, performance and order continuity during a move. Their support documentation turns migration into a checklist: prepare access, transfer data, test before going live, and avoid losing business-critical records during the switch. That mindset is exactly right.
Agency-switching advice adds another important layer. Space Ads frames a safe agency change as a controlled transfer of client-owned accounts, billing, conversion signals, creative rights and operating knowledge. The strongest point is simple: one team needs clear authority at every stage. Ambiguous control during a switch is where duplicate edits, broken tracking and budget mistakes happen.
BidX is useful from the marketplace-advertising side. Its restructuring service talks about organising Amazon ad accounts for transparency, control and long-term profitability. Its onboarding content also points out a practical detail many teams forget: tool data does not always appear instantly, and historical data windows matter. If a platform imports only a certain lookback period or updates campaigns once per day, the first week after migration should be governed more carefully than a normal week.
Reddit seller threads are less polished and more revealing. Sellers worry about agency fees, vague promises, bad campaign foundations, fake reviews and losing control of accounts. Some sellers are happy to pay serious retainers when an agency brings more capability than one in-house hire. Others feel they paid thousands per month for routine bid changes and generic reports. The lesson is not “agency good” or “agency bad”. The lesson is that the handover must transfer judgement, not just activity.
What most advice misses: the first 14 days are commercially weird
A website migration has a go-live moment. A marketplace ad service migration has a messy overlap period. Attribution is still settling. Search terms are still arriving. Old bid changes are still affecting auction eligibility. Stock positions may have changed since the last report. A campaign paused by the previous agency may have been paused for a reason that is not visible in the ad console.
That is why the first two weeks should be treated as a profit cutover window, not a performance sprint. If the incoming operator tries to prove value immediately by changing every bid, rebuilding every campaign and relaunching every discovery lane, they may erase the very evidence they need to understand the account.
The better rule is boring but profitable: during the first 14 days, change only what has a clear commercial reason. Fix broken access. Stop spend that lost permission. Restore campaigns that were wrongly capped. But do not restructure the entire account before the margin, stock and search-term history have been reconciled.
The five ledgers every migration needs
A good cutover ledger does not need to be pretty. It needs to be specific. I like five tabs.
1. SKU profit permission
For every advertised SKU or product family, record selling price, marketplace fee estimate, fulfilment cost, COGS, return reserve, contribution margin before ads, break-even ACOS and current permission label. Use plain labels: Scale, Protect, Learn, Hold, Fix or Stop.
This is where FiveX fits naturally. Our profitability dashboards connect marketplace revenue, fees, ad spend, inventory and margin so the ad operator is not guessing which products can afford traffic. If a SKU has €11.20 contribution margin before ads, it should not be managed with the same ACOS target as a SKU with €4.10.
2. Search-term memory
Export winners, blockers and watchlist terms. Include the reason, not only the term. “wireless charger fast” might be a winner for an Amazon.nl hero SKU at 16% ACOS, a watchlist term on bol.com because conversion drops outside promotion weeks, and a blocker on MediaMarkt because shoppers expect a bundle the listing does not include.
3. Budget and pacing rules
Record monthly budget, daily caps, campaign roles and the moments where spend must be protected. A €5K account does not need theatrical budget complexity. It does need to know that branded defence must not die at 14:00, that launch campaigns have a fixed loss limit, and that low-margin discovery cannot borrow budget from profitable exact campaigns without approval.
4. Stock and offer vetoes
Ads should not scale when the offer is commercially broken. Record stock cover, inbound dates, Buy Box or offer eligibility, fulfilment mode, price position and listing issues. FiveX inventory insights help here because the advertising team can see when a campaign is about to create the wrong kind of success: demand the warehouse cannot fulfil profitably.
5. Decision rights
Write down who can pause, who can reduce bids, who can change budgets, who can restructure campaigns and who approves marketplace-level reallocations. If this is not explicit, the migration creates a polite traffic jam. The old agency hesitates, the new operator waits, finance asks for a report, and spend keeps leaking because nobody owns the decision.
Named example 1: NorthSea Coffee moves €5K from a generalist agency
NorthSea Coffee sells espresso accessories across Amazon.nl and bol.com. Monthly marketplace ad spend is €5,000: €3,200 on Amazon, €1,800 on bol. The generalist agency reports 4.1 ROAS and wants to “scale the winners”. The new marketplace ad service receives the account and notices the hero tamper has a €29.95 price, €8.40 marketplace and fulfilment cost, €9.10 COGS, €1.20 return reserve and €11.25 contribution margin before ads. Break-even ACOS is about 37.6%.
So far, lovely. But the cutover ledger shows the exact campaign on Amazon has been running at 22% ACOS, while bol discovery is spending €420 per month at 39% ACOS on a lower-margin gift bundle. The new operator does not rebuild everything. First move: protect Amazon exact and branded defence until 22:00, cap bol discovery at €10 per day, and move €300 into a bol exact lane only for terms that already produced orders below 28% ACOS.
The result after 30 days is not glamorous, which is why I like it: spend stays near €5,000, revenue dips 3%, but contribution profit after ads improves by €690 because the account stopped buying low-quality discovery clicks during the handover.
Named example 2: VoltEdge restarts MediaMarkt without losing Amazon
VoltEdge sells USB-C hubs on Amazon.de, bol.com and MediaMarkt. The incoming operator sees a tempting MediaMarkt opportunity: low competition, strong electronics intent and a retailer account manager asking for more budget. The old account has €1,200 per month assigned to MediaMarkt but spends only €450.
Without a cutover ledger, the obvious move is to increase MediaMarkt budgets. With the ledger, the picture changes. The MediaMarkt SKU has €6.80 contribution margin before ads, only 18 days of stock and a 9% return reserve because compatibility questions create returns. Amazon exact campaigns for the same product have a 19% ACOS and 42 days of stock. If MediaMarkt suddenly scales, it may steal inventory from the more profitable Amazon lane.
The migration rule becomes: MediaMarkt can test up to €25 per day for 10 days, but only while stock cover stays above 14 days and CPC stays below €0.42. FiveX advertising automation can enforce that kind of guardrail by connecting performance rules with SKU economics instead of letting the platform chase spend in isolation.
Named example 3: LunaPet preserves a negative keyword that looked wrong
LunaPet sells premium dog beds on bol.com and Amazon.nl. During migration, the incoming specialist finds “orthopedic dog bed large” added as a negative phrase in an Amazon campaign. At first glance, that looks absurd. It is one of the category’s strongest buying-intent terms.
The search-term ledger explains the story. The term spent €310 in three weeks with no profitable orders because the large size was out of stock twice and the listing had a delivery promise problem. On bol.com, the same term converted at 24% ACOS when LVB stock was healthy. The right action is not to delete the negative blindly. It is to relaunch the term in a probation campaign with a €15 daily cap, only after Amazon stock is above 21 days and the delivery promise is back below three days.
That is the migration lesson in miniature: the ad console shows the setting. The ledger explains the scar tissue.
The 14-day marketplace ad service cutover plan
Days 1-2: freeze and collect
Freeze non-urgent structural changes. Collect campaign exports, search-term reports, placement reports, budget history, invoices, SKU margin data, stock cover, offer status and previous reporting decks. Confirm that the brand owns the ad accounts, billing access and historical data. If an old agency owns any critical asset, solve that before optimisation begins.
Days 3-5: reconcile profit before performance
Match advertised products to SKU margin. Identify products where reported ROAS is healthy but contribution margin is weak. Mark campaigns that should not spend until stock, price, listing or Buy Box issues are fixed. This is where FiveX AI recommendations can help the operator prioritise exceptions instead of reading 47 tabs like a detective with too much coffee.
Days 6-10: make only permission-based changes
Adjust budgets and bids only where the commercial reason is clear. Reduce spend on products below margin threshold. Protect campaigns that are profitable and stock-safe. Put uncertain terms into probation instead of deleting them. Keep a change log with date, reason and expected effect.
Days 11-14: approve the first operating model
By the end of the cutover window, the new service should present a simple operating model: weekly decision cadence, SKU permission labels, budget lanes, escalation rules, testing budget and reporting format. If the only output is “we optimised bids”, the migration is not finished. It has merely become busy.
What to ask a new marketplace advertising service before migration
- Which campaign settings will you freeze during the first 14 days?
- How will you calculate SKU-level break-even ACOS before changing budgets?
- How will you preserve search-term winners, blockers and watchlists?
- What stock, offer or listing issues can veto ad spend?
- Who has authority to pause, reduce, scale or restructure campaigns?
- How will you separate Amazon, bol and MediaMarkt decisions when one SKU shares inventory?
- What will the first 30-day report show beyond ROAS and ACOS?
The practical takeaway
A marketplace ad service migration is not successful because access worked and campaigns stayed live. That is the minimum. A successful migration preserves the account’s profit memory: which products can afford traffic, which terms deserve trust, which budgets need protection, which stock positions can support demand, and which decisions need human approval.
If you are moving Amazon, bol or MediaMarkt advertising to a new operator, do not ask them to optimise on day one. Ask them to prove they understand what must not be broken. The fastest way to improve an account is sometimes to spend two weeks refusing the wrong changes. Not flashy. Very profitable. My favourite kind of boring.