Will my date on the free trial transfer over to a new plan or will it be lost?

How are you?

First off, since you indicated that you have a free year trial, I simply want to share that free trials in both QuickBooks Online (QBO) and QuickBooks Desktop (QBDT) are only good for 30 days. In your instance, you might've not noticed that the free trial has already ended as we still have read-only access to our expired accounts. 

Nonetheless, your subscription will immediately include the data from your free trial account. When attempting to switch, make sure you're not on the QuickBooks website's official plans and pricing page because doing so will result in the creation of a new account.

To have the option to downgrade or upgrade, we must ensure that we are logged into the expired account. I'll demonstrate how:

1. Click the Gear icon, and then select Account and settings.
2. Go to the Billing & Subscription tab.
3. Select either Upgrade your plan or Downgrade your plan.
4. Choose your new subscription.
5. Update your billing details.

Just in case you need to make changes to your subscription such as your company details and billing information, you can refer to this article: How to update your subscription and billing details.

Don't hesitate to ping me in the comment section if you need additional assistance in managing your QuickBooks Online subscription. I'm always available to assist you further. Have a great day!

@blackerscarpentr 

You can sign up for a new account for a discounted price and migrate data from the trial account manually. Otherwise, you'll need to pay your trial account the normal price after 30 days to continue.

https://quickbooks.grsm.io/UK