Found a mistake in an old GST return? How to fix it, and how to pay what you owe

If the GST difference is $1,000 or less, or no more than the lower of $10,000 and 2% of that period’s output tax, you can usually fix the mistake in your next GST return. Anything bigger means amending the original return in myIR or making a voluntary disclosure. Telling IRD before it notifies you of an audit can cut any shortfall penalty by 75% to 100%. The extra GST and interest still have to be paid.

That last sentence is where many owners get stuck. Fixing the return is the easy part. Finding the money for two or three periods of under-paid GST, on top of the return due on 28 October, is what keeps people up at night. This guide covers both.

How do mistakes in a GST return usually happen?

Almost always innocently. The ones we hear about most:

• Sales coded wrongly in the accounting software, so GST-inclusive income was treated as exempt or zero-rated.
• GST claimed on private purchases, like a family car or a home renovation, run through the business account.
• Second-hand goods or imported goods handled incorrectly, so input tax was over-claimed.
• A new bookkeeper or new software that mapped accounts differently from the old setup.
• Payments basis versus invoice basis confusion after a change in how the business accounts for GST.

Your accountant often finds it while preparing the annual accounts, or you notice it yourself when a number doesn’t reconcile. Either way, the clock starts when you know. What you do in the next few weeks decides how much it ends up costing.

Can I just fix it in my next return?

For small errors, yes. IRD’s fixing mistakes page allows a correction in the next return if the tax difference is $1,000 or less. You can also use the next return if the difference is no more than the lower of $10,000 or 2% of the GST output tax for the period.

Two conditions apply:

1. It can’t be mainly to delay paying tax. Rolling a known under-payment forward on purpose doesn’t qualify.
2. The test is per return with the error. If the same mistake ran across several periods, look at each one, and talk to your accountant if the total is creeping up.

If you’re over those limits, IRD is clear: “Do not send us a replacement return to fix your mistake.” Instead, amend the original return in myIR if that option is available, or ask IRD to change it. If IRD agrees, it issues a notice of assessment showing the corrected amount.

What is a voluntary disclosure, and why does it matter?

A voluntary disclosure is telling IRD what’s wrong with a return before it finds out some other way. Any business can make one, at any time, through a myIR message, the IR281 form, a phone call, a letter or a visit (IRD).

IRD asks for:

• your IRD number or GST number;
• the reason for the disclosure;
• the tax period or periods affected; and
• any returns still outstanding.

In practice, a disclosure that IRD can act on straight away also sets out the corrected figures and how they were worked out. A disclosure that later proves incomplete can lose its penalty reduction, so if the error is large or spans several periods, get your accountant to quantify it properly first. Don’t let that take months, though. Timing matters more than polish.

How much could the penalty be?

When a return understates tax, IRD can charge a shortfall penalty on top of the tax. The size depends on how the mistake happened (IRD shortfall penalties):

Behaviour	Shortfall penalty
Not taking reasonable care	20% of the shortfall
Gross carelessness	40%
Abusive tax position	100%
Evasion	150%

The “unacceptable tax position” penalty, also 20%, applies only to income tax shortfalls over both $50,000 and 1% of the return’s total tax, so it rarely touches a GST error. For the honest coding mistakes above, “not taking reasonable care” is the one in play.

How much can a voluntary disclosure reduce it?

A lot, if you’re early. IRD’s page on lowering your shortfall penalty sets out the reductions:

When you tell IRD	Possible reduction
Before the first notice of a pending audit or investigation	75% to 100%
After that notice, but before the audit starts	40%
During a registration check or unannounced visit	40%
During an audit, about a different tax type	75% to 100% for that other tax

There are two more reductions worth knowing:

• Good behaviour. A penalty can be halved if you haven’t paid a shortfall penalty for the same tax type recently. For GST, PAYE, FBT and RWT the look-back is 2 years; for other taxes it’s 4.
• Temporary shortfall. If the error reverses itself, for example a timing mistake that corrects in a later period, the penalty can be reduced by 75%, provided the correction happens within 4 years.

The message from IRD is simple: tell it “as soon as you can”. A disclosure made the week before an audit letter arrives is worth far more than one made the week after.

Already know the corrected figure is more than you can cover? Check your funding options in 60 seconds. There’s no credit check when you first enquire.

What does a voluntary disclosure not fix?

Disclosure reduces penalties. It doesn’t reduce the tax, and it doesn’t stop interest.

• The GST itself is owed in full, just as if the return had been right first time.
• Use-of-money interest runs on under-paid tax because IRD was without the money. A disclosure doesn’t change that, which is why paying quickly is the other half of keeping the cost down. Our page on use-of-money interest explains how it accrues daily.
• Late payment penalties come back into play if the corrected amount isn’t paid by the date IRD sets. That’s 1% the day after the due date and a further 4% on day seven, as explained on our late payment penalties page.

So the real risk isn’t the disclosure. It’s a well-handled disclosure followed by a bill nobody planned for, which slides into the same escalation path as any other GST debt.

A worked example

Illustrative only. Not a real client.

A Napier landscaping company switched accounting software last year. During the year-end review, its accountant finds that $92,000 of GST-inclusive sales across three two-monthly periods had been coded as exempt. The GST missed is $92,000 × 3/23, or $12,000.

• Next return? No. Each period’s error is around $4,000, well over $1,000 and over 2% of that period’s output tax, so the returns need amending.
• Penalty exposure. This looks like not taking reasonable care: 20% of $12,000, or $2,400.
• Disclosure. The accountant makes a full voluntary disclosure through myIR within a fortnight, before any contact from IRD. That puts the company in line for a 75% to 100% reduction. With no GST shortfall penalty in the past 2 years, the good behaviour reduction is also on the table.
• What’s still owed. The $12,000, plus use-of-money interest back to when each period was due.

The penalty is largely handled. The cash isn’t. The company’s 28 October return is also due, and January brings another GST period alongside provisional tax. The directors have three realistic choices for the $12,000: pay it from reserves, ask IRD for an instalment arrangement, or borrow and clear it in one go. Our arrangement vs loan cost check puts the last two side by side in dollars.

Paying the corrected amount: your options

Once IRD confirms the amount and the date it’s due, the options look the same as for any IRD balance:

1. Pay in full from cash flow. Cheapest if you can do it without starving the business of working capital.
2. An instalment arrangement. IRD will consider one for disclosed tax. While you keep to it, late payment penalties stop, though interest continues. You’ll need your other returns filed and to stay current on new tax, and a missed instalment can unwind it (IRD).
3. A loan that clears IRD in one payment. IRD’s interest and penalties on that balance stop, and you repay a lender on known terms instead. This suits larger corrections, businesses already juggling other tax, or owners who want IRD out of the picture before the January payments land.
4. Penalty remission, separately, if part of the problem was outside your control. See penalty remission for when IRD can remove penalties.

Many businesses combine routes, such as a short arrangement for part and funding for the rest. Our loans to clear IRD debt page explains how the funding side works.

Putting it right, start to finish

Finding an error in a past return feels like being caught out. It isn’t. Owners who put it right quickly usually come through with little or no penalty. The part that needs planning is paying the corrected amount without creating a new problem.

That’s our day-to-day work. We help New Zealand business owners clear IRD balances all the time, and a fresh assessment after a voluntary disclosure is exactly the kind of debt we’re comfortable looking at. Loans run from $5,000 to $5,000,000 for business purposes, and property-secured funding can be possible in as little as 24 hours.

The enquiry form takes about 60 seconds, and there’s no credit check when you first enquire. We don’t send your details to a pile of lenders, so you won’t be fielding calls from people you’ve never heard of. A real person who knows how IRD works reads your enquiry and calls you back. Please fill the form in accurately: the corrected GST amount, any other IRD balances, how the business is trading and any property you could use. That way the first conversation can point you to the right option.

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