What is close drift?

Written by an ACA-qualified finance manager · about the author · Last reviewed 1 July 2026

A term worth having a name for: the gap between the numbers you signed off and what your ledger says today. Here’s what causes it, why it’s more common than you’d think, and how to measure it.

The one-line definition

Close drift is any change to a balance-sheet figure that happens after the period it belongs to was signed off. You locked September, sent the pack, moved on - and three weeks later someone posts a bill dated back into September. The balance you reported hasn’t just been superseded, it’s drifted away from what you told people it was, silently, with nobody informed.

It’s not the same as an error. An error is something wrong at the point of sign-off. Drift happens to a number that was right when you signed it off - and stops being right afterwards, without anyone deciding that it should.

Where it comes from

• Backdated entries. A bill, invoice or journal posted with an effective date inside a period you’ve already closed.
• Corrections. Someone fixing a genuine mistake, dated back to where it belongs - legitimate, but invisible unless someone’s watching.
• Integrations syncing late. A payments app, an e-commerce platform, or a payroll sync posting historic transactions days or weeks after the fact.
• Lifted lock dates. An admin opens a closed period to fix one thing, and either forgets to re-lock it or someone else posts into the gap.

None of these are unusual or malicious. That’s exactly why drift is so common - it’s the ordinary mechanics of a live ledger, not a rare failure.

Why it matters more than it looks

A few pounds of drift on an immaterial account is nothing. The problem is that drift doesn’t announce its own size - you only find out how big it was once you go looking. And because a Xero balance sheet is cumulative, one backdated entry doesn’t just move the month it lands in; it moves every period since, including ones you signed off months ago. A single change can quietly touch a board pack, a set of filed comparatives, and a lender covenant calculation all at once.

How to measure it

You can’t manage what you don’t measure, and most businesses have never actually measured their own close drift - they just hope it’s not happening. The only reliable way is to compare what a period looked like at sign-off against what it looks like now, across every closed month, and see what moved. That comparison is the whole idea behind Postlock’s free closed-months check: connect Xero read-only and see, in one pass, every document posted into your last six closed months after the fact - what moved, who posted it, and by how much.

How to stop it recurring

You can’t prevent drift entirely - Xero’s lock dates are a soft control, not a vault (see Xero lock dates explained). What you can do is stop it being silent: snapshot every balance at sign-off, and watch for anything that moves afterwards. That turns close drift from something you discover by accident, months later, into something you’re told about the next morning.

Frequently asked questions

Is close drift the same as an accounting error?

No. An error is wrong at the moment you sign off. Drift happens to a number that was correct at sign-off and changes afterwards - through a backdated entry, a correction, or a late-syncing integration - without anyone deciding the reported figure should change.

How common is close drift?

More common than most finance teams realise, precisely because nobody’s normally watching for it. Backdated bills, corrections and integration syncs are ordinary parts of running a ledger - the drift they cause only becomes visible once someone compares sign-off to today.

How do I check how much close drift my business has?

Compare your signed-off balances against live Xero for each of your recent closed periods. The free closed-months check does this in one pass - connect Xero read-only and see everything posted into your last 6 closed months after the fact, with amounts and dates.