In decreasing order of certainty:

1. If you're a staunch nationalist (or even more surely if you're a xenophobe), you'll feel (a lot) better about yourself. Psychological well-being is important.


2. If you work (or intend to work) in a field dealing with border/customs/phytosanitary etc., Brexit may have new job opportunities.



3. If your job/income was somehow threatened by potential immigrants from the EU, it might be less so.




4. If national legislation on environment or other business regulations gets streamlined relative to the EU-inherited one, you might benefit if you're in a business that can take advantage of that streamlining.



5. If you work in a field that the UK government will be more protectionist of (in terms of imports), you might make more money.


6. Something similar for subsidized exports.

Those last two or three items are more contingent on no-deal Brexit, in which the UK will be completely unencumbered by EU with any sort of customs union sooner.

As you can see I can't envisage unconditional benefits. If you look at the reasons why people voted for Brexit, you'll see that my 1, 3 & 4 are based on that. I'm not sure if "not sending money to the EU" (another reason why some voted for Brexit) will translate into any personal financial benefits, given the potential for an economic downturn that might offset any gains from that non-contribution. But one could phrase that as a conditional benefit as well.

The elephant in the room is of course how will British economy react (in the short run, since this is focus of the OP's question) to whatever flavor of Brexit passes. Unless you choose to trust the arch-Brexiteers' positive forecasts, the prognostic from more established sources is negative, e.g. Standard & Poors predicted UK recession until 2020 in case of a no-deal Brexit

S&P's analysis sees a recession lasting four to five quarters should there be no deal before the exit date on 29 March.

It sees the economy shrinking 1.2% in 2019 and 1.5% in 2020, and returning to only moderate growth the following year so that by 2021 economic output would still be 5.5% lower than in the event of an "orderly exit and transition period".

Of course analysts aren't infaillible. But in this case I haven't heard from a non-politicized body saying UK will shrug it off.

There will be no immediate benefits, or even in the short term.

It may be possible to do trade deals with other countries that the EU would take longer to complete, but they are likely to be unfavourable to the UK due to the difficult situation and reduced bargaining power post-brexit. Also, any benefit from them will only come once they have offset whatever is lost when the UK leaves the EU and the Common Market / customs union.

There may be some small gains in sovereignty, in that the UK could pass some laws that are currently incompatible with EU regulations. Practically it won't want to make major changes that make trading more difficult. It will also be under pressure to accept rules from other countries in exchange for trade deals (mutual recognition of rules is the basis of trade deals), or to make its economy more competitive with non-EU economies (e.g. by removing worker's rights).

The UK will be able to control immigration from the EU. It already has full control of non-EU immigration. Demands to reduce immigration will cause worker shortages and economic loss. While some may regard reduced immigration as a benefit, it's a largely intangible one where as the monetary losses are very real.

There may be some benefits for certain parts of the UK. For example, Scotland may be able to achieve independence due to increased support after being forced to leave the EU against its collective will. There will be considerable disruption during the process but in the medium term it may have benefits. It's difficult to tell as there are so many unknowns.

As I'm sure you've probably worked out, there's no definitive, general answer to this question. For evidence, I'll simply point to the fact that, if there was, it would have been shouted from the rooftops by pro-Brexit campaigners.

However, it's possible to sketch out some of the likely consequences but you'll have to work out for yourself if you consider them net positive or not.

Firstly, assuming we don't remain in the customs union, we'll be able to negotiate bi-lateral trade deals. Short term, this is unlikely to have much effect. The reason being that there are a lot to complete so most are being negotiated on a like for like basis i.e. the same as our current EU ones. Just for stability.

In the medium term (and 5 years is probably there or thereabouts) we'd be expecting to close final version of some of the bigger ones e.g. US, EU, China, Switzerland. It's unlikely that the EU trade agreement will be net positive for the UK because they'll keep their usual red lines and we'll have our own, different, ones.

For the others, though, there are opportunities. For example, the EU tends to negotiate very complex agricultural tariffs. This is because of CAP and the general strength of the agricultural lobby in the EU. The downside is that the EU often has to give up some advantage in other areas to maintain this subsidy regime. For the UK, agriculture is substantially less significant, politically. So we may well end up agreeing trade deals that are net negative for our agriculture industry, compared to now, but beneficial to other industries e.g. manufacturing or services. If you're farming rape seed today this could be an issue. If you work in advertising (to pick a random occupation), it could be positive.

No deal has equivalent but different concerns. We'd be under WTO rules. However, the exact tariff regime we'd come up with hasn't been agreed (or at least publicised). Once the initial confusion has died down, there are likely to be winners and losers relative to existing tariffs. My educated guess is that agriculture and services will take a hit which manufacturing may well do better. But it's just a guess at this stage.

Secondly, assuming we don't stay in the single market, there'll be no freedom of movement with the EU. Now, it's highly debatable what level of immigration we'll have post-Brexit. In fact, it's economically questionable if it should be much lower than now. However, what is fairly indisputable is that freedom of movement makes immigration levels difficult to predict and, worse, dependent on circumstances outside of the UK's control. So, if you found your children in schools where there was a substantial increase in pupils, but without the equivalent timely investment, this is less likely to occur in future (whether the school investment will be at an appropriate level in future is a separate question).

Thirdly, the EU has strict rules on state subsidies. Outside of the EU, we are free to choose what we subsidise (ok, probably not completely free as we will likely be constrained by trade agreements but how we are constrained will be our choice). This is something that the current Labour leadership are very keen on as they would like to invest heavily in public ownership. So, if you consider, say, rail nationalisation a positive move then this sort of thing is much easier outside the EU.

And fourthly, don't discount independence considerations. There are plenty of people that do consider a united Ireland or independent Scotland a positive thing. For the former, where once the considerations were primarily religious, post-Brexit, there are likely to be very good economic arguments for uniting Ireland. Would it swing a vote sufficiently? Probably not given the depth of feeling but a major UK recession could affect that.

Similarly in Scotland, there's a much stronger case for a second referendum if Brexit happens than if it didn't. Moreover, the EU was dead against a break up of an EU country. They may well look very differently at a Scotland coming in from the cold, as it were. If Scotland also wanted to join the Euro (toxic during the first referendum, less so now), the EU may be very amenable. This could easily be enough to swing a vote.

The Brexiters have made multiple claims about benefits... None of them had much merit IMHO, but the main ones were:

Reclaim full sovereignty

There are two main gripes here:

The first is that Brussels produces laws that apply as is (Regulations) or that set a minimum standard that must get transcribed into national law (Directives). EU citizens have a say on them by virtue of the EP; the UK government has some form of say on them by virtue of the EU Council and how EU commissioners get appointed; the UK's (or any other member's) national parliament has no say. The net result of this setup is that EU institutions tend to be viewed as not democratic enough.

A corollary argument that latches on to this first point is that, without these apparently annoying EU regulations -- that prevent you from e.g. eating chlorinated chicken, working 60 hour weeks, drinking polluted water, or buying lead-laced toys -- the UK could improve the living standards of its poorer population by working more and lowering its standards to cut the cost of goods. You can hear this lower cost of goods argument being made straight from Rees-Mogg's mouth, albeit without the part that makes explicit that it would involve cutting standards and corners.

The other is that the European Court of Justice supersedes all national law according to the ECJ. In practice it's a bit murkier, because the constitutional courts of at least one member state (France [FR]) have politely begged to differ with the ECJ and held that their constitution trumped EU law should a test arise.

At any rate, the threat to sovereignty should be fairly clear if you're concerned that an EU high court, set up to be the arbiter of EU treaties (that your government signed and your MPs approved) and laws (that you're involved in making through the EP), with one judge appointed by each member state, actually does its job and enforces that an EU treaty or law (part of international public law) might supersede your national law (as it should, bar your Constitution).

Independent trade deal policy

The gripe here is simple: the EU is currently responsible for negotiating international trade deals on its members' behalf. And the UK would like to make its own deals. The UK's silver-tongued negotiators can presumably do much better. They're reputably so outstanding, and the UK's economy is so important, that negotiating new trade deals will be the easiest thing ever.

Snark aside, an indicator that things might not go as planned here is Turkey: by virtue of having a customs arrangement with the EU, Turkey reportedly has a hard time finding trading partners who want to negotiate deals with it. The reason is that, as a would-be trading partner, you're better off negotiating with the EU instead, giving you access to a much bigger market, while snatching a de facto deal with Turkey as a bonus without the latter having much if any say on it.

That, you might be thinking, is an excellent reason to not stay in the Customs Union, on top of the pesky problem of not having any independent trade policy if you're in it to begin with. But then you'd also introduce a lot of trade friction with the world's largest market, and risk a return of The Troubles by introducing a hard border at the Irish border.

EU contributions

This argument was famously advanced on London buses, but it's been so debunked and ridiculed by now (to say nothing about retracted the day after the Brexit poll) that I hope you don't need any convincing it was hogwash.

Still, I would raise in passing that whether the UK continues to pay into EU contributions or not in the future (which it might, if it ultimately opts for a Norway type of deal), there are financial commitments that need to be honored short of having wide ranging implications for UK retirees (former EU civil servants), UK students (Erasmus), UK research programs and infrastructure projects that rely on EU grants and subsidies, and so forth.

Border control

Until now the UK already had control over its borders when it came to non-EU migration. So what we're actually talking about here is preventing the proverbial Polish plumber from settling in the UK, or the UK doing its part to absorb the millions of Syrians that poured into the EU owing to a crisis that the UK played its part in fueling.

IMHO this might actually be the only tangible benefit -- provided that you view that as a good thing, and think that having no freedom of movement for UK citizens within the EU is an acceptable cost.

The problem with seeing benefits is that the main benefit of Brexit is that it gives more power to our politicians to decide things themselves, for good or bad. This means that any benefits are only as good as the politicians making them, and may also be impacted by any deal we strike with the EU.

Also, in the short term (which for something of this scale probably means 3-5 years), the costs of change may outweigh benefits. Also, as in any change, benefits will be distributed unequally across the population; if your job relies on the EU, then you'll probably lose, but if it depends on non-EU connections, you may gain.

Sadly, it's often the poorest who are least able to adapt to change (due to a lack of cash reserves and/or difficulties in reskilling, finding new work, etc.), so – baring government policies to the contrary – the benefits are naturally more likely to go to the better-off. Note that this isn't unique to Brexit; this is the case for any change.

Unfortunately, whilst there's many possible immediate benefits, neither Tories nor Labour have made it clear what they'd actually do with their new freedoms, so the rest of this is more suggestions rather than actual policies anyone's suggested. I suspect that both parties have ideas, but don't want to publicise them yet as they don't want to be seen as pro-brexit, and as they don't want to show their cards to the EU until any deal is sealed.

We could, for example, drop import tarifs on a wide range of goods from food to technology, dropping their prices instantly. However, it's unlikely that politicians will do this as it looks like we'll either be in a customs union, or some similar equivalent, to ease the NI issue.

Trade deals (which would help our exports) unfortunately will take time, and the EU exit rules prevent us negotiating new deals until after we leave (which does seem unfair – imagine not being allowed to look for a new job / flat until after you'd left your old one...!), so unless there's been some behind-the-scenes negotiating, those will take time, particularly those with larger nations (though Trump might on a whim tweet us one immediately...!).

Staffing in hospitals etc. won't be directly affected, as those with jobs will continue to have them (though they may decide to leave themselves). However, this is one area where we should be able to show benefits within a few years. Assuming that the home office controls (currently only non-EU) immigration, so as to limit total (EU + non-EU) immigration to some 'acceptable' level, then a reduction in EU immigration would allow them to increase non-EU immigration, whilst hitting the same total levels. If we have more control over immigration, we could for maintain/reduce overall immigration, but prioritise health workers from anywhere in the world over EU workers in any industry. This requires political willpower, but would probably be a political win – they would be able to bring in more health workers whilst also reducing immigration.

We could pass stricter rules on health/safety on food and goods, but this would make it harder to import goods (in particular, if our rules are stricter than the EU, then most EU producers would need to adapt to meet them), so is unlikely to happen. It's more likely we may relax some over-strict rules to allow cheaper imports from a wider range of countries; but no politician wants to be seen to be relaxing H&S rules, so it's not hugely likely.

One significant benefit is that we may be spared the Eurovision song contest...

Some potential benefits that may be unlikely to materialise:

State aid and nationalisation

There are Brexit supporters on all sides of the political spectrum. A socialist Brexit supporter might tell you that the end of European Union competition law, in particular against State aid to privately owned companies. For example, Labour leader Jeremy Corbyn has said:

We cannot be afraid of intervening directly to support supply chains and new industries, any deal with the EU must recognise that the old state aid rules are no longer valid

Likewise, a major programme of nationalising the means of production is likely to cause objection within the European Union.

Of course, many people would question whether this is a benefit.

The socialist newspaper Morning Star supports Brexit for this reason.

Rewilding

If the Common Agricultural Policy ends and UK farmers will lose their subsidies, many UK farms will disappear, in particular unprofitable sheep farming. This is even more true if tariffs are slashed, such has has been proposed. This means sheep would disappear from the hills in the UK, which would open up opportunities for a major rewilding programme, with forests returning where overgrazing currently prevents them. Note that true rewilding would take more than just removing the sheep, but supporters of rewilding may find that opposition to other proposals (such as a reintroduction of predators including wolves) would be less powerful if sheep farmers are history.

I'm not aware of anyone explicitly supporting Brexit for this reason, nor am I aware of anyone who has proposed the policy to effectively end British sheep/hill farming, but it may be an unintended side effect which some people may consider beneficial.

Needless to say, most people would consider it a strong negative point if British farms disappeared, and most likely post-Brexit domestic policy would ensure that they don't.

Comment: Although some on the (far) left support Brexit, in practice the Brexit agenda is being set by pro-free market, anti-immigration, nationalist forces, that are rather associated with the political right than with the political left. It is probably unlikely that the above points will actually materialise.

Until the terms of the exit are agreed to, it will be impossible to answer this concretely. What is certain is that many of the purported benefits were, at best, not fully thought-through and will never come to be. With anything relating to trade, the EU is the UK's primary trade partner, and the UK will still have to comply with EU regulations in order to export to EU countries. This will merely add complication and a layer of bureaucracy to the matter.

I think the economic consensus is that the UK will be economically worse off for leaving. We can be reasonably sure that a disorderly no-deal Brexit will be economically disastrous, so everyone reasonable wants to avoid that. Even the heterodox Economists for Brexit say UK manufacturing will have to be wound down like coal and steel were (which I sincerely hope doesn't come true). Of course the economy wasn't the sole factor in the vote to leave - although I think some Brexiteers were and are, shall we say, 'overly optimistic' about the post-Brexit economy.

The intangible benefits in principle are sovereignty - all our laws will be made domestically, we won't have to implement or abide by laws made by supranational entities - and control over immigration. But in practice our exercise of these benefits will be circumscribed by agreements and trade with other countries.

India for example wants easier immigration for Indian nationals to the UK in its trade deal with the UK. We can change our laws about goods and services but in international trade we must nevertheless meet the standards set out in the trade agreements. We will continue to be subject to non-domestic courts or arbitration bodies formed to adjudicate disputes per the conditions of our international agreements.

It is difficult to predict how such things will affect the individual citizen or household, particularly as there is no formal agreement yet. The only things on the table are the draft withdrawal agreement or no deal (i.e. trade under WTO rules).

Wanting to control immigration doesn't make me a xenophobe. It means we have less tax consumers, we build less houses on greenfield sites, and we stress our health sevices and schools less.
We need skilled workers, and we get these through grants of work visas.

Surgeons, yes. Baristas and car washers, no.

But, there's no will to control immigration- as it's seen as xenophobic to do so.
So, we might as well stay if nobody is getting what they want.

yes yes, I'm sure this will get deleted as it's bound to offend someone somewhere.

More control over immigration

This is the most quoted reason by leavers for leaving the EU. With reduced immigration, the probability of you meeting someone who doesn't speak perfect English or the probability of segregated communities (i.e. in Bradford) being created are decreased. Secondly, reduced immigration will lead to a slowdown in the increase of the population - more land will be available per person (so less homes will need to be built on greenfield land) and less demand will be placed on public services (schools, hospitals etc.). Finally, the immigration policy of Britain can better represent the economic needs of the country - due to the reduced immigration from the EU, we might be able to relax immigration restrictions from the rest of the world.

British sovereignty over laws and trade

The available options for parliament to legislate will drastically increase. Britain will be able to pass very left wing budgets (of the likes of Italy's) or pass very right wing programmes of reducing product safety standards or workers rights and not have the EU interfering. Britain will also be allowed to enforce its own tariffs on goods from abroad, which is a good thing if you are a protectionist.

No money going to the EU budget

Some money (not as much as claimed) will be available to spend as we will not be contributing it to the EU budget.

No consensus. All claimed benefits are strongly disputed.

However, claimed benefits include:

Increased independence of action.
Increased political and economic nationalism.
Lower immigration.
Less ‘red tape’.
Lower contributions to European budgets.
Being able to make trade deals.
Laws are proposed by people elected by the people
Other more ironic ‘benefits’ include:

Britons coming to see what the EU actually does.
The collapse of UKIP.
‘Rebalancing’ the economy away from financial services.
Lower house prices, more tourists, and other consequences of a weak currency/economy.
Europe running more smoothly without the awkward British.
Less competition for European companies.
Jobs for lawyers.