Another wiring question: could I splice a neutral wire from a power socket for the SMART light switch?

The power socket is just next to the light switch.
As with most people, the light switch does not have a neutral wire.
Could I just splice the neutral from the adjacent (literally just next to it) for the light switch (to SMART it)?

As long as it is the same circuit, you should be fine.

On the other hand: Are you allowed to do fixed installations to electric circuitry? I am as I’m an electrician but for non-electrician it’s stricly unlawfull to do fixed installations in Finland and actually all EU-area.

Generally in North America you are allowed to do work on residential property you own without a license, although you may need a permit depending on the work performed. You can’t do it for anyone else or in a rental that you live in. Some jurisdictions may prohibit it.

How would anyone ever know who did the work?

To clarify: when you say “right next to it” you mean in the same junction box? If that is true, then in 90% of cases you should be OK. If not, there is an excellent chance that you are looking at separate circuits.

I ask because other than in a bathroom or kitchen an outlet and switch in the same junction box would be unusual.

Depending on where you live in the US you may or may not be allowed to make changes to the wiring inside the walls without an electrician’s license. However, I do not know of any place in the US that prohibits a homeowner from changing fixtures within or attached to an existing junction box.

yes u r right… it is very unusual for this particular switch of mine… not sure why it was designed so…

Oh, you’re in the UK. Ignore everything I’ve said, I have no idea of wiring conventions over there.

ETA: I really wish the new board software would include a poster’s location on the actual post like the old software did.

Im actually based in South East Asia and we are allowed to do minor wiring ourselves too.

I think generally, internal wiring should be the same (I hope!)?

I’m out too, I have no advice for non-North American wiring.

First question - 240V or 120V?

I assume then your wiring for neutral is like N.American 240 high powered wiring.(Red, black 240V AC, white neutral)
I would be worried why there is no neutral. Are all your light bulbs 240V (Ours are all 120V. 240 is for things like ovens and clothes dryers, or a Tesla charger - which oddly, does not use the neutral.
The other possibility (unlikely) is that it’s 3-phase power.

Does the smart switch actually need the neutral? Do you have a multimeter - what’s the voltage between the two live wires, and from each wire to neutral? (240V and 120V AC, I assume)

If you can’t answer the questions about how the power is connected, maybe monkeying with the wire is not a good idea.

We are 240V. Unfortunately in Asia the standards are not strongly enforced - even the modern houses still don’t come with neutrals for switches. This is apparently a big problem in China as well. It takes some effort to run a neutral back to light switch when it is not needed at all.

Smart switches ideally require a neutral to keep it constantly powered.

North American 240V does not use 3 wires (not counting ground), it uses two wires. It only requires the two line (ungrounded conductor) wires for 240V phase-to-phase. 120V/240V connections add the neutral (official the grounded conductor) to give you 120 between either line and neutral, typically to power the electronics, motors, lights etc. In an oven or dryer 240V is only used for the heating elements.

I would bet money that European or Asian colors are not the same as American colors, though of course you never know what kind of madman did the wiring. White neutral? Current IEC is blue. The old UK neutral was black. Better to grab a tester, or, best, a professional if you are not sure.

so you have a wire leaving the light switch to go to the light. You have one wire going directly to the outlet. How many other wires enter? You need one more wire to supply the light switch. Does it enter from the ^power panel or does it come from the receptacle box? If the power panel, where does the 2nd wire for the receptacle come from, the ^power panel or the light switch?

^power panel in this instance is someplace like an upstream junction box or the actual panel.

Light switch: just 1 wire (live) enter and 1 wire (to light) exit.

As for power panel, the live appears to come from source.
(There are some assumptions made here, as a lot of these wires are concealed).
I also assumed they are from same circuit as they react to the same circuit breaker.

I received a suggestion to just draw the live, neutral from the power panel - then I am guaranteed no problems.

so you are saying the wires that go to the outlet are totally separate from the wires that go to the light switch. But they are on the same breaker. Yes you can run a new supply and neutral to the light switch but how difficult is it. I hesitate telling you it sounds OK to use the neutral from the outlet without seeing it and testing it myself.

For US wiring, no neutral wire at a switch is extremely common and perfectly fine as ordinary mechanical switches don’t need, nor have a place to connect a neutral.

The wiring configuration is called a switch loop - the incoming hot and neutral are in the ceiling wiring box at the light fixture. A single romex runs to the switch location - the always-hot wire is black, the switched wire is the romex’s white wire with a wrap of tape around the ends to signify it’s not a neutral. This switched hot connects to the light.

Or, as a minor variant, if you’re in a place that doesn’t use romex, such as Chicago, you’ll have a conduit run to the switch containing an always-hot black wire and a switched wire of some other color (usually red) back to the light. At least with that, you can fish a neutral to power a smart switch.