He would not say if Ms Reeves is looking at further tax cuts to give her more headroom after months of economic downturn, and said the "big decisions" on tax were made in the October budget.
"But as I have said before, in terms of the big decisions on tax obviously the budget was the place that we took those decisions - but as ever, going into a statement I am not going to say in advance what we might do and what we might not do.
The OBR is required to produce two economic forecasts a year, but, the chancellor said she would only give one budget a year to provide stability and certainty on upcoming tax changes.
Sir Keir Starmer said the government was in the "early stages" of looking at whether tax rises or spending cuts were needed to meet Labour's self-imposed fiscal rules.
Ms Reeves could extend a freeze on income tax bands and allowances beyond April 2028, dragging more people into paying more tax as their pay rises.
