You are about to read proposals to solve the perennial problem of the black labour market or undeclared work.Many people are probably not even enthusiastic about solving this problem, but the main benefits of a significant reduction in undeclared work are new jobs, more tax collection which could have many positive effects (reduction of certain taxes, reduction of the national debt, vignette prices, etc.).
There are probably no accurate or even approximate calculations of how much this type of work exists in Slovenia.
As a layman, I do not know what powers inspectors have in detecting this type of criminal activity, but the legislation should allow the following methods of work:
1. the inspector comes to the employer and introduces himself as a natural person asking for illegal work.     If the employer agrees to this and agrees to pay, the conduct would be criminalised (the process would be recorded to gather incriminating evidence).
2. the inspector authorises a natural person (under 18-24 years of age - this is where most undeclared work takes place) to carry out the employer's pre-screening test for undeclared work. The authorised person introduces himself/herself as a natural person asking for undeclared work. An inspector would listen to the test nearby (via listening devices) and if the employer agrees to this form of work and agrees to pay, the inspector would approach (the process would be recorded to gather incriminating evidence).
In my opinion, in the vast majority of cases where mainly smaller companies and sole traders in a mainly service industry provide a service to private individuals, they do not invoice. This is, of course, difficult to detect, but even in these cases the inspectors should have the power to present themselves to a company as a natural person, to arrange some imaginary transaction without an invoice. They could even rent an apartment where they could bring an employee of a company and arrange for some transaction (for example, the replacement of electrical wiring) in the apartment.
Ultimately, if the state significantly reduced the informal economy, it would have a lot more money. The fact that it is not always spent wisely is another problem. So please do not write something positive about the shadow economy.