Figures showed the Treasury has borrowed nearly 10% less so far this financial year than in 2012/13 and prompted economists to predict the 2013/14 deficit will undershoot official estimates by up to £15 billion.
They will come as a boost to the Chancellor ahead of further data later this week expected to show continuing improvement in overall economic growth.
The new figures from the Office for National Statistics showed borrowing dropped from £12.1bn in September 2012 to £11.1bn for September this year - with the figures stripping out the distorting effect of bank bail-outs.
Martin Beck, of Capital Economics, said: "Although the economic recovery has taken its time to come though in the fiscal numbers, September's figures suggest that the public finances are now beginning to reap the rewards of a stronger economy. Meanwhile, the recovery in the housing market is boosting the Government's coffers."
Public finances were boosted by tax receipts up 7% to £44.8bn, including an increase in stamp duty from £588 million to £817m. Receipts from income tax were up 11% to £11.3bn, while VAT and corporation tax takes also rose.
It means the deficit from April to the end of September stands at £56.7bn, down 9.4% on the same period in the previous financial year.
James Knightley of ING Bank said the figures were "fractionally better than expected".
Howard Archer of IHS Global Insight said: "It is looking ever more likely that the Chancellor will significantly undershoot his 2013/14 fiscal targets.
"The hope is that the trend in the public finances will increasingly improve over the coming months as improved economic activity increasingly feeds through to boost tax revenues and help limit benefit payments."