Note that this depends on the jurisdiction. In england-and-wales, it is not illegal to give legal advice other than in specific cases.
Reserved and non-reserved legal activities
Section 14(1) of the Legal Services Act 2007 provides that you need to be entitled to carry out "reserved legal activities". Entitled here means that are either authorised or exempt in accordance with section 13.
Section 12(1) provides:
In this Act “reserved legal activity” means (a) the exercise of a
right of audience; (b) the conduct of litigation; (c) reserved
instrument activities;(d) probate activities; (e) notarial activities;
(f) the administration of oaths.
Section 12(3) defines legal activities as (emphasis added):
(a) an activity which is a reserved legal activity within the meaning
of this Act as originally enacted, and (b) any other activity which
consists of one or both of the following (i) the provision of legal
advice or assistance in connection with the application of the law or
with any form of resolution of legal disputes; (ii) the provision of
representation in connection with any matter concerning the
application of the law or any form of resolution of legal disputes.
So, legal advice is a legal activity but not a reserved legal activity and as a general rule can therefore be carried out without authorisation.
This general rule is subject to a couple of exceptions.
Section 84(1) of the Immigration and Asylum Act 1999 provides that "no person may provide immigration advice or immigration services unless he is a qualified person." In this context, giving general advice is fine; it's giving advice which relates to a particular individual in relation to certain types of immigration matters (e.g. asylum claims, citizenship applications) which is prohibited. See the definition of "immigration advice" and "relevant matters" in section 82(1) for more details.
There are exceptions to this exception (i.e. circumstances in which you can give immigration advice without being qualified) as set out in section 84(4)(d) and various secondary legislation passed in accordance with that section, but none of them are likely to be relevant to an average layperson.
Claims management activities
Certain types of legal advice are regulated by the Financial Conduct Authority. Section 19(1) of the Financial Services and Markets Act 2000 provides:
No person may carry on a regulated activity in the United Kingdom, or
purport to do so, unless he is (a) an authorised person; or (b) an
Section 22(1B) provides that:
An activity is also a regulated activity for the purposes of this Act
if it is an activity of a specified kind which (a) is carried on by
way of business in Great Britain, and (b) is, or relates to, claims
Section 22(5) provides that "'Specified' means specified in an order made by the Treasury". Articles 89F(1) and 89H - 89M of the Financial Services and Markets Act 2000 (Regualted Activities) Order 2001 provide that "advising a claimant or potential claimant" is a specified activity in relation to the following:
- Personal injury claims
- Financial services or financial product claims
- Housing disrepair claims
- Claims for a "specified benefit" (see Article 89(f)(2)(f) for what this means)
- Criminal injury claims
- Employment related claims
Exceptions exist (subject to various conditions) for legal professionals, charities, and other categories again not likely to be relevant for average laypersons.
Note that "carried on by way of business" above means that it is legal to give claims management advice to your friend or relative etc. so long as you are not doing so commercially.
Just because you can give legal advice doesn't necessary mean that you should. There is a lot that can go wrong for a layperson who (perhaps after some Google research) may believe they understand the law. Professionals maintain expensive subscriptions to databases such as Westlaw and Practical Law in order to fully research their topics of expertise, including all relevant statutory provisions and case law. The law is constantly evolving and what was good law yesterday can be reversed by a new statute or a higher court. The legal databases are kept up to date in a way that is almost impossible for a layperson to achieve by themselves. While free alternatives exist such as BAILLI for cases and https://www.legislation.gov.uk/ for statutes, the former has a lot of gaps and the latter contains many out-of-date provisions which have subsequently been amended or repealed but not updated on the site. I'm not aware of any free resources (for English law) which are of a high enough quality for a professional to rely on.
If you're giving legal advice commercially as a non-qualified person, then you are probably dealing with consumers as your clients (since businesses are more likely to want someone profesionally qualified). Sections 49(1) and 57(1) of the Consumer Rights Act 2015 provide that "every contract to supply a service is to be treated as including a term that the trader must perform the service with reasonable care and skill" and "a term of a contract to supply services is not binding on the consumer to the extent that it would exclude the trader's liability arising under section 49 (service to be performed with reasonable care and skill)."
In my view you are unlikely to be able to provide legal advice with reasonable care and skill unless at a minimum you have some legal training and access to up-to-date databases. It's certainly possible to do that without being legally qualified - that's what the paralegal profession is.