This year’s Budget is to be earlier than usual to avoid clashing with the final stage of Brexit negotiations in November.
The date of the Budget, 29 October, also fits in with ministers’ availability and official data releases, a Treasury spokesman said.
The Budget will also be a week after a high profile Brussels Brexit summit, and is expected to be a means to reassure markets.
Mr Hammond gave the date in a tweet.
He said the government’s “balanced approach” to the economy is “getting debt falling”.
Budgets are traditionally given on a Wednesday.
This year the Wednesday in the final week of October is Halloween, although the BBC understands that this was not a factor in choosing the Monday of that week to deliver the Budget.