Source: Sharecast
The ONS said HM Revenue & Customs had alerted it about inaccuracies in the VAT receipts used by the statistics agency when it estimates government borrowing.
As a result, estimates of public borrowing have been out by between £200m and £500m every month since January.
The ONS has therefore cut its estimate for borrowing in the current fiscal year by £2bn, to £83.8bn, and by £1bn for the previous fiscal year.
The revision will be welcomed by chancellor Rachel Reeves, although it remains above the £72.4bn forecast by the Office for Budget Responsibility.
But it is a further blow to the ONS, which has been rocked by a series of mistakes and inaccuracies across its statistical bulletins, leading to criticism from both politicians and the Bank of England.
April’s inflation figures were overestimated and August's monthly retail sales data had to be postponed. The methodology used to compile its labour data has also long come under fire.
The ONS said full details of the borrowing revisions would be incorporated into the next public finances data, which is due to be published on 21 October.
James Benford, director general for surveys and economic and social statistics at the ONS, said in a blog post: "Over the coming weeks, we will work together with the OBR and our data suppliers to identify steps to ensure processes within the data suppliers are robust and the mechanisms to understand and challenge what is provided to the ONS are as strong as possible."
HMRC confirmed it had identified an error in its VAT cash receipts but did not provide further details.
