Takes me about an hour to do the same in the UK and half of that is trying to remember how to log in and do it.
You can send in your tax documents digitally and there are decent software packages to help you do it correctly. For most people it shouldn’t take more than a couple of hours a year. That is for your typical employee. If you’re running a corporation, do not try to file your taxes without a tax advisor.
There are some tax benefits which are only accessible if you file taxes but if you don't want to take advantage of these tax benefits you don't have to file them. In general you also get 5 years to do it.
Also, it's not unlikely that the government is printing the electronically filed information in the traditional paper format to be able to process it the traditional way. (maybe not for taxes, but it's surely the case for some other processes.)
But I agree that "3 months" is probably the time required to collect information, not the time needed to summarize the information for the government. Some banks take a couple of months to send the required yearly investment income/taxes-paid statement.
There's certainly a lot of improvement possible, but for simple cases it's pretty easy already (if you've done it at least once before).
Adding information from the employer is data that the employer has already submitted. Investment data could be transmitted from banks to the tax office directly, instead it's paper, as it always has been for the traditional process. The only iformation that would require filing is such not created through parties that are transmitting data anyway. e.g. private loans, collecting rent, etc.
As soon as any information is required to be transmitted, all information is required.
It's a process designed for execution on paper put into a computer. It's not a process designed for full automation. If any private company would operate that way they wouldn't be making any money.
But it is true.
> I recommend your friend to find good tax advisor if he/she is not capable to do it by himself/herself.
The situation is just as bad in the US. And I would be surprised if it isn't similarly Byzantine in the UK.
A few years ago the federal administrative court recalled tax reforms because nobody could understand them. That's a Normenklarheitsgebotverstoß!