Importing GA4 Key Events into Google Ads: When to Do It, and the Trap Waiting at the End

Importing a GA4 key event into Google Ads takes about ninety seconds and is often the right call. It is also the single most common way accounts end up counting the same conversion twice, bidding on inflated numbers for months before anyone reconciles against the order table. The setup is easy. Knowing when not to use it is the valuable part.

First, the naming change

Google renamed GA4 “conversions” to “key events”. The distinction is now deliberate and useful:

• A key event is a GA4 concept. It is an event you marked as important for measurement.
• A conversion is a Google Ads concept. It is something you are willing to bid on.

Importing is the act of promoting the first into the second. Those are genuinely different decisions, and the rename exists because people were treating them as one.

When importing is the right choice

• The conversion is a GA4-native idea. Engaged sessions, scroll depth, a sequence of events. These do not exist as a page you can put a tag on.
• You need one definition everywhere. If the business already agrees on what a qualified lead is in GA4, importing stops a second, slightly different definition appearing in Google Ads.
• You cannot modify the site. No developer access, no tag manager, but GA4 is already collecting. Importing uses what is already there.

When the Google Ads tag is the better choice

• The conversion has revenue attached.The Google Ads tag can carry a transaction-specific value and an order ID, which gives you deduplication and accurate revenue. Imported events are summarised through GA4's model first.
• You want enhanced conversions. Enhanced conversions attach to a Google Ads conversion action with its own tag, not to an imported GA4 event.
• You need speed. Imported conversions arrive with more latency, which matters for Smart Bidding on short cycles.

The setup

1. Link the properties. In GA4 Admin, under Product Links, link the Google Ads account. You need Editor on the GA4 property and admin access on the Google Ads account; having only one is where most people stop.
2. Mark the event as a key event. In GA4 Admin under Events, toggle the event on. It must have fired at least once to appear.
3. Wait. Newly marked key events are not immediately available to import. A day is normal.
4. Import in Google Ads. Goals, then Conversions, then New conversion action, then Import, then Google Analytics 4 properties. Pick the event.
5. Decide Primary or Secondary. This is the setting that matters most and gets the least thought. Primary actions are what Smart Bidding optimises toward. Secondary actions are recorded and reported but not bid on. Importing six key events and leaving them all Primary means bidding toward a blend of newsletter signups and purchases.

The trap: counting everything twice

Here is the sequence that plays out constantly. A Google Ads conversion tag is already on the thank-you page, set up a year ago. GA4 is also recording a purchase event on that page. Someone imports the GA4 key event because it appears in a list and looks useful.

Google Ads now has two conversion actions firing for the same event. If both are Primary, reported conversions double and the bidding algorithm optimises toward a number that does not exist. Nothing warns you, because from Google's side these are two legitimately configured actions.

The check:open your conversion actions and list what each one actually measures, in plain words, rather than by its name. Two entries that both mean “someone completed checkout” is the problem, regardless of how differently they are labelled. Keep one as Primary and demote the other to Secondary rather than deleting it, so you keep the history.

Why the numbers will not match, and which to trust

Even with exactly one source, Google Ads and GA4 will report different totals for the same thing. This is expected, and the reasons are structural:

• Attribution timing. Google Ads credits a conversion to the date of the click. GA4 credits it to the date of the conversion. A click on Monday converting on Thursday appears in different columns in each tool. This alone explains most day-level mismatch.
• Attribution model.GA4 reports through its own model. Google Ads applies the conversion action's model. Neither is wrong.
• Scope. GA4 counts conversions from every traffic source. Google Ads counts only those it can tie to an ad interaction.

For bidding decisions, use Google Ads. For understanding behaviour across all channels, use GA4. Reconciling them to the same number is not a solvable problem, and time spent trying is time taken from the discrepancies that are real.

Value and currency: the quiet downgrade

If you bid on value rather than on conversion count, this section is the reason to think twice about importing.

An imported conversion carries whatever value GA4 recorded on the event. That depends on your purchase event sending a value and a currency correctly, every time, which is a bigger assumption than it sounds. Three things commonly go wrong:

• Missing currency. GA4 drops revenue entirely on a purchase event with a value and no currency. The conversion still counts; the revenue is simply absent, and Value-based bidding sees a zero.
• Mixed currencies.A store selling in several currencies sends several, and the import has to reconcile them against the Google Ads account currency. Conversion happens at Google's rate, not yours.
• Tax and shipping. Whether these are inside the value is a decision made in the tag, usually years ago, usually undocumented. Two conversion actions measuring the same purchase can legitimately report different revenue for this reason alone.

With the Google Ads tag you control the value at the moment of the conversion and can send a transaction ID alongside it. With an import, you inherit whatever GA4 concluded. For count-based bidding this rarely matters. For value-based bidding it matters a great deal.

Modelled conversions in the chain

GA4 applies behavioural modelling where consent is denied and data is incomplete. That is reasonable for understanding trends, and it means some portion of a GA4 key event total is estimated rather than observed.

When you import that key event into Google Ads, you are importing a figure that already contains modelling, into a system that applies its own modelling on top. The result is usable for optimisation and genuinely poor for reconciliation. If someone asks why Google Ads conversions do not match the order table to the unit, this layered estimation is a large part of the answer, and no amount of configuration will collapse the two.

The practical rule: import for bidding, never for finance. Keep at least one conversion path that is observed end to end, so there is a number in the account that corresponds to something that definitely happened.

When an import stops working

Imports fail in ways that produce no error anywhere. The symptom is always the same: conversions that used to arrive stop, and the conversion action drifts toward an inactive state.

• The product link was removed. Often during an access tidy-up when someone leaves. The link disappears and the import goes with it.
• The key event was renamed. GA4 matches on event name. A developer renaming generate_lead to lead_submittedhas, from Google Ads' point of view, ended the old event and started a new one that nothing imports.
• The key event toggle was turned off during a GA4 cleanup.
• The GA4 property stopped collecting. A tag removed in a site deployment ends both GA4 reporting and every conversion imported from it, in one go. This is the worst version, because it takes out several conversion actions at once.

Google Ads eventually flags a conversion action with no recent conversions, but “eventually” is up to 30 days, and Smart Bidding spends that whole window adjusting to a signal that is quietly gone.

The 30-day inactive problem

Google Ads marks a conversion action inactive when it has recorded nothing for 30 days. For imported conversions this creates a slow failure that is worth understanding, because the timing works against you at every step.

Say a developer renames the GA4 event on the 1st. The import stops that day. Smart Bidding keeps running, and for the first week or two the historical data is recent enough that performance looks normal. By week three the algorithm is adjusting to an account where this conversion has apparently stopped happening, so it reallocates budget away from the campaigns that were driving it. Only on day 30 does Google Ads surface a status change, and by then you have a month of distorted bidding to unwind.

The reason this hurts more for imports than for tags is that there is no symptom on the website. A broken Google Ads tag can be caught by loading the thank-you page and watching the network panel. A broken import involves no browser request at all: the site is fine, GA4 is fine, and the link between two Google products is the only thing that changed.

A low-tech safeguard that costs nothing: when importing, write down the exact GA4 event name in the conversion action's description field. It turns an invisible dependency into something the next person can read without having to open GA4 and guess.

The practical safeguard

Importing creates a dependency chain: your site fires an event, GA4 records it, the product link survives, Google Ads imports it, bidding uses it. Four links, each maintained by different people, none of which raises an alarm when it breaks.

Checking it by hand means opening two products per account on a schedule nobody keeps. Taglert watches Google Ads conversion actions and GA4 data freshness together and emails you when either changes state, so a renamed event on a Tuesday does not become a month of bidding on nothing. The FAQ covers what it checks.