Sitting in the House of Commons to talk about the impact of Brexit is not my typical Tuesday afternoon. But last month I was invited to do just that with the All Party Parliamentary Group for Responsible Tax, alongside MPs Nicky Morgan and Frank Field, as well former HMRC official Judith Knott.

Brexit impacts on virtually every area of the UK economy but one area that hasn't received nearly as much attention as it deserves is tax. That's partly because the UK already sets most of its own tax policy.

However, some of the tax-related changes could come at significant costs for businesses and individuals if the government doesn't get them right. Equally, Brexit offers opportunities and impetus to improve the UK's tax policy. If we don't act now we risk missing out on the opportunities and failing to avert the risks.

So here are the six tax-related areas I asked Parliamentarians to focus on to make sure the UK makes the most of Brexit.

1) Speed up customs clearance: Once we've left the EU customs clearance formalities will apply and could have a significant impact on business costs. Items imported from EU countries become subject to Import VAT, which is likely to incur cash-flow costs. What's more, all goods will need to be Customs cleared. This process can be both time-consuming and relatively costly, with fees typically paid per shipment to a freight forwarder. There's also a whole series of other issues to consider, including the disruption to supply chains, storage space at UK ports, a shortage of freight forwarding agents and trained Customs officers. What we need in the longer term are technological solutions where, for instance, all shipments are securely bar coded allowing them to be Customs cleared with minimal human intervention.

2) Stick to a one step transition period: Businesses want to see transition periods aligned so that they can make one wholesale change to processes and systems instead of a number of gradual, burdensome changes.

3) Support UK productivity: Increasing investment in people and assets can improve productivity. I'd recommend the government considers a number of tax measures to encourage such investment, such as enhanced tax reliefs for staff training costs, which could be targeted to particular types of training, geographical locations, or age groups. To get more companies investing I'd also advise increasing the generosity of the capital allowances regime and improving UK tax relief for investment in intangible assets (the UK lags behind other EU countries like The Netherlands and Ireland).

4) Preserve the flexible labour market: Last summer's Taylor Review highlighted the UK's strong labour market performance, characterised by rapid job creation, high female participation levels and low unemployment. Tax can play a key role in shaping a flexible labour market. Rules regarding employment versus self-employment status should allow for this flexibility while also protecting exchequer revenues. There also needs to be a place for genuine entrepreneurial activities and we have seen how tax reliefs, such as entrepreneurs relief, have had a positive impact.

5) Maintain HMRC service levels: Clients tell us, and we know from our own experience, that HMRC is one of the most professional tax authorities in the world. However, I would agree with HMRC Chief Executive Jon Thompson that it isn't realistic to do everything they are doing now as well as all the additional work arising from Brexit without more resource. Funding needs to be allocated to recruit extra staff to implement Brexit changes.

6) Put in place principles of good tax policy: The fundamental principles behind making good tax policy should remain post Brexit. The report by the Chartered Institute of Taxation, Institute for Fiscal Studies and Institute for Government set out recommendations, including clear guiding principles and priorities for tax policy, improving consultation before key decisions are made, using external review to open up a public debate and enhancing Parliament's (and the public's) ability to scrutinise tax proposals. The aim of these changes is better-designed measures and a more coherent tax system commanding wider public support. I would urge the Government to consider these recommendations. 

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