When the chancellor sits down, the Office for Budget Responsibility (OBR) will publish economic forecasts for the next five years.
It will set out whether the government is likely to meet the rules it has set for managing the public finances, and how the economy is expected to perform.
Its judgement on the government’s plans is keenly watched by financial markets and can have a significant impact on confidence, in turn affecting government borrowing costs.
Leader of the Opposition Kemi Badenoch will respond to the speech in the House of Commons.
MPs then debate the measures for three days before voting on them.
If approved by MPs, tax changes can come into effect immediately.
However, the government must pass a finance bill to make them permanent.