Tax calculation is the dependency nobody thinks about until checkout starts erroring. Over the 180 days ending July 2026, TaxJar ran clean (100%, A+, zero major incidents), Vertex posted 99.93% (A) with 2 incidents totaling 124 minutes, and Avalara posted 99.87% (B+) with 2 incidents totaling 212 minutes.
The numbers, side by side
| Metric (180 days ending July 2026) | TaxJar | Avalara | Vertex |
|---|---|---|---|
| Uptime (major/critical incidents) | 100% | 99.87% | 99.93% |
| StatusBird reliability grade | A+ | B+ | A |
| Major or critical incidents | 0 | 2 | 2 |
| Total downtime | 0 minutes | 212 minutes | 124 minutes |
How these numbers are measured: StatusBird checks each service's status every 2 minutes, around the clock. Uptime counts major and critical incidents over the 180 days ending July 2026; brief degraded periods are excluded so chronically noisy status pages do not distort the comparison. Full details on the methodology page.
How reliable is TaxJar?
Zero major incidents in the window. History on the TaxJar reliability page and in is TaxJar reliable.
How reliable is Avalara?
Two incidents totaling about 3.5 hours. Avalara sits in the checkout path for many mid-market and Shopify Plus stores, where a tax-calc timeout can present as a generic checkout error. Details: Avalara reliability page and is Avalara reliable.
How reliable is Vertex?
Two shorter incidents, A grade. History on the Vertex reliability page.
Why tax outages are the sneakiest checkout killers
When a tax API fails, most checkouts do not say "tax provider down"; they show a generic error or an infinite spinner at the address step. Merchants then debug their theme, their apps, and their payment gateway before anyone thinks to check the tax service. If your store calculates tax through a third party, put it on your monitoring list next to your payment provider; the diagnostic order in why is my Shopify checkout not working applies here too.
Start monitoring your stack free with StatusBird: 3 services, no credit card required. Pro is $29/month for all 84 services with SMS, email, Slack, Teams, and Discord alerts within 2 minutes of a status change.