Even if there is a no deal Brexit, the UK will still have to make payments to Brussels, the Chancellor has told MPs on the Treasury Committee.
The UK has agreed a formula with the EU about payments post-Brexit, Mr Hammond said, but that this was on the assumption there would be a deal.
If there was not a deal that might change but it was "not plausible" that if there was not a deal no money would be paid.
But, he said, that the EU would rather not receive a payment in a lump sum so this could be a point of leverage in negotiations.
Brexit deal dividend ?
Philip Hammond has been asked by the Treasury Committee about whether there will be a Brexit deal dividend.
If there is a "good deal" business confidence could rise and consumers have the confidence to spend, the Chancellor said.
" It would be choice, say in 2021 if we had a deal agreed, signed and sealed everybody was happy, business confidence was rising, it would be a choice.. in 2021 whether to maintain £15bn of
headroom to the fiscal rule or whether to borrow a little more and put a little
more into the spending review. That would be a choice we could make".
He added that the UK would not be sending £9bn or £10bn a year to Brussels and the OBR had assumed this would be spent on items that the EU would be doing, such as agriculture.
He defined a good deal as one that involved frictionless trade continuing.
Philip Hammond has been asked by the MPs on the Treasury Committee about the digital tax announced in last week's budget.
The 2% tax is on sales - not profits - by large social media platforms, internet marketplaces and search engines from April 2020.
Mr Hammond said that ensuring the tax was proportionate and "does not transgress our
obligations under international tax laws" was very important.
He added that the tax was not an on-line sales tax.
While it was reasonable to argue that an on-line sales tax should be considered, he said that high street stores also had on-line sales.
Growth v surplus
Philip Hammond has also touched on ways to reduce the UK's debt during his evidence session with the Treasury Committee.
The "smart way" to shrink debt as a proportion of GDP was faster economic growth, rising living standards and growth in wages, the Chancellor said.
The harder way was trying to run a budget surplus and pay off debt.
Brexit deal headroom - Hammond
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Philip Hammond has told the Treasury Committee that public spending could increase if there is a deal to leave the EU.
"In the event of a successful negotiated exit deal with the
European Union I would expect confidence to return to the UK
economy very quickly".
"I would expect us to no longer need to hold the kind of
level of headroom against meeting our fiscal rule in 2021 and
indeed, it's not just a single year - we've got a profile of
headroom against that metric across the whole five year period.
We could, if we chose to, allow borrowing to rise a little and
eat into that headroom and that would be a choice."
'No love' for fixed odd betting machines
Sports minister Tracey Crouch resigned last week over "delays" to a crackdown on maximum stakes for fixed-odds betting machines.
Philip Hammond has been asked about this at the Treasury Committee where he has told MPs that the decision to implement the cut in stakes from £100 to £2 would in October 2019 was taken because the change needed to be managed in an "orderly and sensible" way.
"I have absolutely no love for these machines. They are terrible things".
But thousands of jobs will go in the gambling industry and jobs losses needed to be conducted on a voluntary basis.
Nicky Morgan, who chairs the committee, says that the changes were expected to kick in from April 2019.
Philip Hammond has added, though, at his appearance at the Treasury Committee that he has not abandoned his aim to achieve a budget surplus in
the next decade.
"No it hasn't been abandoned."
"I have said since the autumn of 2016 that I would operate a
balanced approach, recognising the need to reduce and ultimately
eliminate the deficit in order to get debt falling sustainably,
something we have now achieved."
End of austerity?
What does an end to austerity mean, Nicky Morgan asks Philip Hammond.
The Chancellor replies that it not just about public spending rising.
Real wages need to grow which in turn implies sustained economic growth, he tells the MPs on the Treasury Committee.
Now a top House Republican, Kevin Brady - who helped shepherd a new US tax cut through Congress last year - calla the proposal "troubling" and hints at retaliation if the UK or other countries proceed alone.
"The ongoing global dialogue on the digital economy through the OECD framework should not be pre-empted by unilateral actions that will result in double taxation," he says.
"If the United Kingdom or other countries proceed, that will prompt a review of our US tax and regulatory approach to determine what actions are appropriate to ensure a
level playing field in global markets.”