My application was refused due to 'lack of evidence of funds', are there hidden requirements for UK visa applications?

Great question. If somebody had asked this about 3 years ago the site would have a lot less redundant information. But on the other hand, we would spend all day marking duplicates and get bored.

The answer to 'are these hidden requirements?' is no. The answer to 'buried somewhere I didn't look?' is probably yes. They are obvious requirements to practitioners and they know where to look. ECO's get special training and a manual so it's easy for them to know where to look. To an end-user, like an applicant in say, India, they wouldn't know where to look, and so these requirements might seem 'hidden'.

When you study entry clearances in a formal setting, like a law course, they give you an overview, the big picture. The 'big picture' means that the visa rules cannot exist alone in a vacuum, they have to coexist with all the other legislation Parliament makes. Plus the rules have to be fair for everyone and it wouldn't be fair to give visa applicants exemptions that native Brits don't have.

Some of the important acts that come into play when you see visa refusals are...

• The Housing Act 1985 (accommodation)
• The Local Authority Social Services Act 1970 (access to public funds)
• The Rehabilitation of Offenders Act 1974 (criminal history)
• The Commissioners for Revenue and Customs Act 2005 (legality of funds)

And a big one that your question exposes...

The Financial Services and Markets Act 2000 (money laundering, provenance of funds)

Native Brits have to abide the same rules and if something shows up in their bank accounts that appears out-of-whack, they get investigated and sometimes into serious trouble. Parliament's view is that visa applicants should not be exempted and so ECO's get trained to investigate those areas. Legal practitioners get trained when they take courses/training and so generally speaking, legal practitioners and ECO's are on the same wavelength. Coincidentally, that's why it's important to use a solicitor that's registered with the Law Society; it keeps both sides on the same wavelength.

Within the same money laundering/provenance of funds regime, they also have a list of banks they don't like. If somebody submits statements from one of those banks (or they figure out that somebody has an account at one of those banks), then the app will be refused (and they will use a different reason so that their sources are not compromised).

There is no conspiracy to keep all of these things secret. To my knowledge, it's a universal condition that countries do not make visa rules inside of a vacuum. Adding... Parliament does not make the rules in the Schengen zone, but they do not like to be wildly out-of-sync with the EEA in lots of areas. So if there's relevant legislation in the UK, there is a good chance there will be counterparts on the continent. People who are aware of the rules in one jurisdiction will have an edge in a neighboring one.

Also, UKVI is not required to list out ALL the relevant laws on their site because it would be too ponderous. They do, however, advise people to use a practitioner if their application is not straightforward. If you try to complain, they will reply that more than 90% of applications world-wide are successful.

So yes, sometimes the end-user is left having to find out these 'hidden' requirements the hard way. When in doubt, contact a lawyer.

Note: all applicants should read the guidance for specific things to include in their application.

Gayot Fow has provided a great answer with detailed explanation of why the rules exist and where (possibly) to search for them. What may not be so clear from his answer is that for any visa application, the applicant needs to show that he/she would be able to support themselves while in the UK, without having to rely on the assistance of the state (i.e. you won't end up a burden to them).

The requirement of the proof of funds is very clearly stated in all guidance documents for the visa. In many (most?) cases, the applicant would be providing proof of their own income, savings or some other source of funds, as they would be paying for the trip themselves. In some cases (like in yours), there will be somebody else covering the expenses of the trip - which is not very uncommon. What is important is that the proof of available funds is submitted with the application, regardless of whether you are paying yourself or somebody else is paying for you.

The electricity bills will prove that you will likely have somewhere to live, not that there are money available to pay for your food, transport, etc.

Note further that you are required to provide the history of funds, not just the proof at the last moment. This will normally be at least three (but sometimes more) months worth of proof - e.g. bank statements, payment slips, etc.

As a personal example, I myself live in the UK and regularly sponsor relatives to visit me in the UK (at least once a year for the past 10 years). With their visa application, they submit my last three bank statements (from the UK bank) plus my employment confirmation letter from my employer (in the UK), plus a hand-written letter from myself explaining the circumstances and stating that I will be covering the expense of their trip to the UK.