Switching Google Ads agency without a slump: hand over first, then rebuild

Why a switch is not an optimisation project

For a retailer, an agency switch is first and foremost a measurement problem. In my assessment, most of the slumps that happen during a switch are caused not by campaigns but by the infrastructure behind them: a billing setup tied to the old agency, conversion actions sitting in the agency's manager account, remarketing lists that suddenly no longer exist. If the new agency rebuilds structure, bid strategies and feed at the same time, nobody can say afterwards what cost the revenue.

Hence the basic rule: nothing gets rebuilt during the handover. Hand over first, then check whether the figures hold, then rebuild. Even agencies that want to win switching clients themselves recommend a parallel run without changes. From the retailer's point of view, what matters is being able to trace cause and effect: only if exactly one thing changes in a given phase will you know afterwards which thing it was.

What do I secure before the cut-over date?

Before you give notice, establish what belongs to you and what is tied to the agency's manager account. Whether you own the account is the first check, covered in detail in who owns the Google Ads account. For the switch itself, this list is enough:

For Google Ads, Analytics and Merchant Center, Google describes the same transfer route: add a person with admin rights, then remove the old access. For Merchant Center, Google says you may need to contact support. That is the point I would settle first, because it can take the longest.

How to give the new agency access without creating new dependencies is covered in granting Google Ads access to third parties safely.

The three places where the move costs performance

Billing setup

According to Google, billing is an account-level link between the advertising account and a payments account. If the agency bills through its manager account, that link is tied to the agency. If the account is on monthly invoicing and the old agency's manager account is the paying manager, the ads stop serving as soon as it is unlinked. According to Google, the billing setup has to be changed before unlinking. With a credit card or direct debit set up directly in the client account, the problem does not arise.

Conversion actions in the manager account

Many agencies use cross-account conversion tracking: the conversion actions sit in the manager account, not in the client account. According to Google, after unlinking these actions stop recording conversions for new clicks, and for earlier clicks only for the remainder of the conversion window. If the client account's own tag is still installed, it resumes counting. On top of that, when switching between cross-account and account-specific actions, campaigns that optimise towards a specific action move to the default conversion goals.

For a shop, this means Smart Bidding suddenly optimises towards a different goal, or towards no data at all, without anyone touching a campaign. Google advises checking that your own tags are still on the website before switching back, and removing old actions and tags only after the conversion window has passed. Your own conversion actions should therefore be in place and counting before the account is unlinked.

Audiences from the manager account

If the account uses the agency's remarketing tag or shared lists, those lists stop populating after unlinking and the account loses access to them. According to Google, ad groups that target these lists and campaigns that exclude them stop running. The exclusion is the silent trap: a new customer campaign that excludes existing customers via an agency list comes to a halt.

How does the billing transfer work?

Google calls the process Change Who Pays. The request is made by an admin of the current paying manager account, which usually means the old agency. They enter the 10-digit ID of the new manager account and choose a date or "As soon as possible". The new agency then has 7 days to approve the request, otherwise it is cancelled and has to be submitted again.

With monthly invoicing, further approvals are needed: the primary contact of the payments profile has to approve changes, and the admin or primary contact of the destination profile has to accept agreements by email. In practice, that means three parties with deadlines. I would therefore set the transfer date on a fixed day when everyone is available, not on "As soon as possible" in a holiday week.

When should you tell the old agency?

Once you know the list above, but before any technical step is needed that only the agency can trigger. For the billing setup this order is mandatory, because the request comes from the current paying manager account. My assessment: combine the written notice with a handover list and a cut-over date, use the notice period in the contract, and during that time ask the old agency for no further changes to the account apart from the handover steps. If you have settled access and ownership in advance, you negotiate from a calm position.

The baseline from shop data

Before the cut-over date, record per week what arrives in the shop, not what Google Ads reports: orders, revenue, new customers, ideally for the last eight to twelve weeks and for the same weeks of the previous year. Add the same weeks from Google Ads: cost, conversions, conversion value.

After the switch, you compare the two series. This gives a simple diagnosis:

• Shop revenue stable, Google Ads conversions falling: measurement is broken, usually conversion actions or tags. Leave the campaigns alone and repair the tracking.
• Both falling by the same amount: demand, season or delivery. Check billing setup, delivery and lists first, then the previous year's weeks.
• Shop revenue falling, costs rising: bids are working towards the wrong goals. Check which conversion goals the campaigns now optimise towards.
• Shop revenue falling, Google Ads conversions stable: the cause more likely lies outside the account, for example in other channels.

How to reconcile shop and account properly is covered in are your conversion figures right?. The baseline is useful for the new agency too: it gets a yardstick it has to be measured against, instead of the old agency's version of what came before.

What do you change in the first 30 days?

As little as possible in the steering system and as much as necessary in the infrastructure. In my view, the following are allowed: repairing broken measurement, fixing disapproved products in the feed, correcting obvious budget errors and excluding search terms that burn money. Account structure, bid strategies, target ROAS, merging campaigns or setting them up from scratch do not belong in this phase.

The reason is in Google's own documentation: after changes to a bid strategy's settings, or when campaigns are added or removed, the strategy enters a learning period, key metrics can fluctuate, and according to Google you are better off evaluating performance only afterwards. Rebuilding during the handover therefore adds a second disruption on top of the first. More in the Smart Bidding learning period.

The new agency uses the time for an audit and a written rebuild plan. I would start rebuilding once shop figures have held at baseline level for two to four weeks. What an audit for this should contain is set out in what a good Google Ads audit has to contain.

When the rule does not apply

Changing nothing is a rule for an account that broadly works. It does not apply if the account demonstrably burns money, for instance because conversions are counted twice or Smart Bidding optimises towards a micro-conversion. In that case the old state is no sensible baseline, and repairing measurement takes priority over calm. Even then, though: one change at a time, each one noted with its date.

In small shops with only a few orders a week, a single week fluctuates so much that two weeks of stability say little. There I would rather wait four to six weeks. And I would postpone a switch directly before the strongest sales season where possible, because that is when any disruption costs the most.

Disclosure

I sell Google Ads management as a freelancer myself, so I benefit from agency switches. With me, the work starts with an audit using read-only access and a written roadmap, and rebuilding comes only after that. The recommendations above are assessments from the retailer's point of view, not an evaluation of individual accounts.