Philip Hammond is making his first major financial statement since taking control of the Treasury.
The Chancellor will reveal the extent of the Brexit black hole as predicted by the independent Office of Budget Responsibility.
He has said the Autumn statement will support the economy “as we begin writing a new chapter in our country’s history”.
It is expected that Mr Hammond will unveil a package of support to help people who are “just about managing” – known in Whitehall as the “Jams” who Theresa May has identified as a priority for support.
Writing on Twitter, Mr Hammond said his focus was on “preparing and supporting” the economy for the future.
His statement begins at 12.30 and our liveblog will keep you up to date with the Chancellor’s announcements and the reaction as it happens.