The Leave camp has gone on the offensive, with a warning the UK faces a "triple whammy" of woe if it votes to stay in the EU on June 23, while Remain has urged voters not to take the risk that Brexit will hit exports, jobs and wages.
So what are the two sides saying?
:: The UK pays £350million a week - or £19billion a year - to the EU, which could be redirected to British priorities, including by spending an additional £100million a week on the NHS.
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:: The UK could face with a "hefty" additional bill from the mid-term review of the EU's 960billion euro (£750billion) budget for 2014-2020, which was held back until after the referendum. Additional costs from the migration crisis could force the budget up by billions of euros.
:: A European Parliament report earlier this year highlighted a backlog of unpaid bills totalling 24.7billion euros (£19.4billion) which the EU will have to pay down. Vote Leave estimates the UK could be asked to fund £2.4billion of these repayments, in line with its 12.5% contribution to EU budgets.
:: Boris Johnson has warned the UK could be forced to bail out Eurozone countries if the crisis in the single currency worsens, with unknown sums potentially at stake. Despite a 2011 agreement that non-Eurozone states will not have to support bailouts of this kind, Vote Leave argues that an article in the EU treaties requiring members to help a country facing "natural disasters or exceptional occurrences beyond its control" could be used to force Britain to chip in.
:: Brexit campaigners argue that sluggish growth in the EU is holding Britain back and free movement of European workers is hurting jobs and wages for UK nationals. They say it will be in EU members' self-interest to continue to trade with the UK following Brexit and that Britain will be able to boost exports by striking new trade deals with countries around the world.
:: The Remain camp rejects Vote Leave's £350million-a-week figure for UK contributions to the EU budget, which was branded "deceitful" by Sir John Major and has twice been ruled "potentially misleading" by the independent chief statistician Sir Andrew Dilnot. Sir Andrew found that the £19billion-a-year figure ignores the UK's £4.4billion rebate and EU cash which comes back to the UK. He put the net contribution in 2014 at £9.9billion - or £190million a week.
:: The UK's EU contribution is anyway only a tiny fraction of Government spending, amounting to less than 1% of national GDP. A Treasury document found that this sum would be dwarfed by the expected 6.2% hit to GDP resulting from Brexit, equivalent to £4,300 for every household in the country.
:: The Treasury analysis found that Brexit would increase unemployment by 520,000-820,000 within two years and that tax receipts would fall by £36billion by 2030. The Treasury says that £250billion worth of UK trade would be at risk.
:: A report by Euler Hermes Economic Research estimated that up to £210billion of foreign investment in the UK could be lost in the four years following Brexit, with the financial sector hardest hit.
:: The Remain camp argues that if Britain wants to maintain access to the European single market, it would have to continue to pay into EU budgets and accept free movement, as Norway does, without having a say over EU policy. If this was rejected, the UK would face a lengthy negotiation to secure partial access in a Canada-style deal, or tariffs on its exports under World Trade Organisation rules.