Economists have said taxes will have to go up in the autumn Budget if the chancellor is to meet her self-imposed rules on borrowing to fund public services.
In her Labour conference speech on Monday, Reeves said the government was facing difficult choices and promised she would not take risks with the public finances.
The chancellor pledged to keep "taxes, inflation and interest rates as low as possible".
But hinting at further tax rises, she said the government's choices had been made "harder" by international events and the "long-term damage" done to the economy.
Labour pledged in its election manifesto not to raise VAT, along with National Insurance, or the basic, higher, or additional rates of income tax.
But newspaper reports have suggested officials at the Treasury are examining broadening the scope of VAT to help raise further revenue.
VAT is levied at a standard rate of 20% on most goods and services in the UK, unless they are classed as reduced or zero-rated.
Most private healthcare services are currently exempt from VAT, apart from some procedures which are classified as being primarily cosmetic.
Private school fees were also previously exempt, but the government introduced VAT on school fees in January, estimating it could raise £1.7bn a year by 2029/30.
