The operating balance excluding losses and gains (obegal) was 11.3%, or $611 million, higher for the 10 months ended April than had been forecast.
The variance was mainly due to ACC actuarial losses being incorrectly classified in ACC's forecast as insurance expenses rather than gains and losses.
At balance date, the obegal was $6 billion compared with the forecast $5.4 billion.
Treasury in March had to release revised financial statements for the seven months ended January after Inland Revenue failed to account for about $600 million in provisional tax accruals during January.
Following that correction, the operating balance was in surplus by $200 million.
It was previously reported as a deficit of $400 million, something Dr Cullen leapt on as a reason to avoid making tax cuts.
In the latest release, after gains and losses were removed, the operating balance was $3.1 billion, 25.3% above the forecast $2.5 billion.
Treasury said the reclassification of ACC losses had no impact on the operating balance.
Treasury said there were three main contributors to the higher-than-expected operating balance:
Investment returns were $800 million higher than forecast due to positive investment returns in April, corporate tax revenue was $300 million higher than forecast and higher-than-expected assessments were lodged in April and were expected to have a positive impact on the end-of-year result.
GST revenue was $600 million lower than forecast, mainly due to a change in GST due dates.
Analysis of the accounts showed that taxation as a percentage of GDP fell slightly in April to 31.9% from a forecast 32.1%.
Most Crown expenses increased in the period with social security and welfare continuing to dominate government spending at $14.6 billion for the 10 months, up 4.3% on forecast.
Health spending increased nearly 10% on forecast to $9.3 billion, education was up 5.9% to $8 billion and law and order was up 13% to $2.4 billion.
The largest percentage increase was in spending on economic and industrial services (up 73.5% to $2.3 billion) followed by heritage, culture and recreation (up 45% to $927 million).
Treasury said social security and welfare spending was offset by lower unemployment benefits, due to an improvement in labour market conditions.
Increased health spending was promised in the 2007 budget to maintain and improve existing service levels and increased education spending was due to higher demand-driven expenses from roll growth.
The other good news for Dr Cullen was more banks yesterday starting to cut their fixed mortgage rates.
ANZ-National Bank, TSB Bank and Kiwibank followed the lead of ASB and Westpac last week of cutting rates after the Reserve Bank indicating the official cash rate would be reduced later this year.
ANZ-National cut is key two-year rate by 0.2% to 9.2% and cut the one-year rate by 0.4% to 9.4%.
The bank's best rates are now at three, four and five-year rates at 9.1%.
Kiwibank cut its three-year term to 9.2% and its four and five-year terms to 9.3%.
TSB has a 9.2% two-year rate and a 9.25% three and four-year rate.
