Paste the balance sheet you reported and a fresh one from Xero. You will see which lines have moved since. No sign-up, no Xero connection, and nothing leaves your browser.
The comparison runs in your browser. Nothing is uploaded, nothing is stored, and there is no account to create - open your network tab and check. This is a working paper you are doing yourself, faster.
A lock date stops accidental posting, and you should use one. It does not tell you what you reported. Nothing in Xero holds a record of the figures in the pack you sent, so when a balance moves after sign-off there is nothing to compare it against - which is why it is usually found a year later, in a comparative column.
This page does that comparison once, by hand, for one month. Postlock does it for every month you sign off, automatically, and tells you the document, the person and the date behind the movement by the next morning.
Read-only. Postlock is technically incapable of changing your Xero data.