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Guide 36 · Ecommerce · GA4 + Tag Manager

Send the begin_checkout event: the first step of checkout, with the cart that is being checked out

Checked 11 November 2026 · Verification: reference file checked in Python (figures recomputed from the worked example) · Steps traced to Google's developer docs and Analytics Help, opened 11 November 2026 · 5-minute read

Begin_checkout opens the checkout funnel: send it when checkout starts, with the full cart and its value, so the purchase journey and checkout journey both have a starting point.

Expected signal

After step 3, DebugView shows a begin_checkout event with value 72.05 and both items in the array, fired once per checkout start. After about 24 hours, the purchase journey and the checkout journey both show the Begin checkout step.

Download the reference: the begin-checkout-event reference (JSON) (1289 bytes, MD5 8c1f6a5379a542e497afd0fd14750e0d). It holds the event parameters, the worked example, and the recomputed figures.

What you need

  • The Google tag on the site. The event is sent through the Google tag; the install guide covers it.
  • Access to the website source code, or a Tag Manager container. The event fires when checkout starts, so it needs the checkout entry point.
  • The cart contents at checkout start. The worked cart is Google's two example items: three Stan and Friends Tees at 10.01 (30.03) and two grey tees at 21.01 (42.02), a cart of 72.05.

The trace

  1. Fire the event when checkout starts. The begin_checkout event measures the first step in the checkout process, so it belongs on the action that starts checkout: clicking the checkout button on the cart page, or loading the first checkout page. Send gtag("event", "begin_checkout", { currency: "USD", value: 72.05, coupon: "SUMMER_FUN", items: [...] }) with the full cart in the items array.
  2. Send the whole cart, with the value to match. The value is the cart total: 10.01 × 3 = 30.03 for the tees, plus 21.01 × 2 = 42.02 for the grey tees, which is 30.03 + 42.02 = 72.05. A begin_checkout carrying one item out of a two-item cart understates the checkout value and breaks the funnel comparison with the purchase that follows.
  3. Send it once per checkout. A visitor who goes back to the cart and starts checkout again produces a second begin_checkout, and that is correct: each checkout attempt is its own step in the funnel. What must not happen is two events for one start, for example one from the button and one from the page load.
  4. Check it in DebugView. Turn on debug mode, start checkout, and open DebugView (Admin, then Data display, then DebugView). Select the begin_checkout event and check the value reads 72.05 and the items array holds both items. One checkout start must produce one event.
  5. Confirm the reports after about 24 hours. Both funnels start from this event: the purchase journey counts it as the Begin checkout step, and the checkout journey uses it as its first step. If either funnel shows checkouts beginning at zero while orders exist, this event is the one that is missing.

Dead ends

DEAD END — BEGIN_CHECKOUT ON THE CART PAGE VIEW. A visitor who views the cart has not started checkout. Firing begin_checkout on the cart page load inflates the Begin checkout step until the funnel shows more checkouts than carts. The event belongs on the start of checkout, not on the view of the cart.

DEAD END — THE PARTIAL CART. A begin_checkout that carries only the first item, or the items after a discount is applied, disagrees with the purchase that follows. The purchase value is compared against the begin_checkout value in the funnel, so the two must describe the same cart.

DEAD END — TWO SENDERS FOR ONE START. A button handler and a page-load trigger that both fire begin_checkout record two checkouts for one visitor. Pick one trigger and remove the other; the funnel counts events, not intentions.

End state

Every checkout start sends one begin_checkout event with the full cart, a numeric value equal to the cart total (30.03 + 42.02 = 72.05), currency USD, and both items in the array. DebugView shows the event the same minute, and after about 24 hours both the purchase journey and the checkout journey count the Begin checkout step.

Sources

Checked 11 November 2026. The event definition above is the one in Google's ecommerce developer guide and the recommended events reference, both opened 11 November 2026. No step was run inside a live Analytics property, because that needs a Google sign-in and this site does not sign in as anyone. The figures were recomputed in Python: 10.01 × 3 = 30.03, 21.01 × 2 = 42.02, and 30.03 + 42.02 = 72.05. The reference file was checked the same way.