Couldn't someone living near a border just go over and buy stuff and skip the tariffs?

They will definitely ask if you purchased anything. You can lie but if you get caught expect little to no leniency.
Can you get away with it? Probably, for some stuff. Is it worth it? You’re rolling some dice, you decide.

Couldn't someone living near a border just go over and buy stuff and skip the tariffs?
Yes, they could. Yes, they can. Yes, they do.
Yes, the ones who do it as a business get caught, eventually ;-)

You will need a fast ship to evade the border patrols. May I suggest the Falcon here. She did the Kessel run in just twelve parsecs.
- Wait, but parsecs are a unit of dis...ohhhh

Believe it or not, straight to jail.
- Only for a few weeks before a judge tells them to release you. And so they send you to a black site in another country with no trial.

OP discovers smuggling.

Come visit the EU. People drive to other countries to get cheap gas and cigarettes all the time. Hell, when I lived near the border, 95% of my groceries were German.
- Yea, I read about Schengen and I love the concept.
  Unfortunately the rest of the world has not been enlightened and still have border control.
  I hope one day, there will be a world-wide Schengen area.
- I live near ze French border in BW and half the customers in the supermarket are French or Swiss.

If they also consume it over the border, sure.
If they bring it back, they are importing it and that’s when you have to pay the tariff. If you’re thinking “just keep it in your trunk how will anyone know?” just consider how long smuggling has been a thing and ask yourself if you think border guards have thought of this. They have.
- Well for some items it's definitely easy. Laptop for example just say it's your laptop. No box or receipt you brought it with you. But it has to be like 1. And it's still illegal.

As I and others have mentioned elsewhere, you're taking a risk doing this, as if you get caught it will cost you more.
One other thing to keep in mind is warranties if anything goes wrong with the item. If you are trying to make it look like you brought the item with you, you'll be getting rid of all the documentation and packaging that proves you purchased it. That includes receipts. Warranties often require proof of purchase, so you may be throwing away your warranty by doing this.
Also, keep in mind that models and model numbers are often different in Canada. I've had phones that were identical to the US model but had a different model number. I've also had phones where they sold the European version in Canada (again with its own model number) and so it was basically a different phone from what you'd get in the States for the same model name (different CPU, different supported communication protocols.)
Often our model numbers will get a "CA" added to the end making it obvious. Sometimes it won't be obvious, but won't match model numbers you can easily find info for online. My current laptop model number is undiscoverable online because it is so rare. There are similar ones for which the info mostly matches my computer, but I'm not always able to find good info.
It's kind of funny watching Americans talk about this now as it was something we Canadians used to talk about all the time... Strategies for buying goods in the US to save money.

Going across the border to buy something is completely legal. Bringing it back for resale is different. You said something you want, and then you said pretend it's a personal item. There's an inconsistency. If it's something you want, then it is a personal item. As long as it isn't illegal, you're legally fine. That being said, there are two things to be aware of. Legality is a bit more fluid these days (especially at the border), and I'd guess you'd look and act very suspicious, which would probably end poorly for you based on the first thing.
I did this often when I was in a country with VAT. It was cheaper to fly, buy the thing, and fly back. Or sail, which I also did.
- I really don't like the way this is worded. It sounds like you're saying that going across the border and buying a "personal" item and not declaring it is just fine.
  Yes it is perfectly legal to go across the border and buy something and bring it back (assuming we're talking about legal goods here, not drugs or contraband items, obviously.)
  But you must declare those items. If you get caught pretending it was an item you brought with you but you actually purchased across the border, you may be fined. When you are asked a bunch of questions by the border guard, they're looking for signs you're lying. If they get a whiff you're lying or uncomfortable, they'll start digging. If they catch you trying to avoid paying the duties on a laptop, not only will you have to pay the duties, you may have to pay a fine on top of that, not to mention every future border crossing you make may be more difficult. If they catch you trying to cheat they are way more likely to implement a fine and put a note on your file.
  There are (for now) certain amounts of money you can spend when you cross the border, which changes based on how long you've been gone, for which you won't be charged duties - but you still have to accurately declare what you've spent!
  
  That's probably a valid point. I just checked the import requirements into the States for citizens, and it does say you need to declare items. I have never bothered, was always asked, and usually said no, or maybe a bottle or two of liquor.
  No wait. The first time I traveled abroad was to Mexico via airplane, and I itemized everything. Including the gummy bears I bought, every coin I had, all currency, a small jar of sand from the beach, and a lot more. I filled up 3 pages. The border cops just rolled their eyes, and verbally told me to only declare anything over $10K. Last time I came into the States via boat, I just said personal stores, and it was also fine.
  If you want to follow the law to the letter, do it to the letter. If you don't get sunburned easily, maybe do that.
  ~~Bear in mind that it's easier to say you fucked up a form than lying to some badge wearing~~
  You know, it's been more than a year since I've been back to the States. Shit's gotten weird there. Listen to more recent anecdotal stuff, read the 6059b form, and decide your risk level.
  Never volunteer information, especially to cops. Otherwise, look at some other comments here. It's probably a more usual use-case. I'm not a good average person.
- Pretty sure this is false in most countries. You are required to disclose purchases and declare values, even for personal use. If they hit a certain thresholds, you'll have to pay a tax.
  Now I'm sure most people just ignore this, because practically they don't know which items you carried with you and which you purchased. But it isn't legal.
  
  Last time I crossed back into the US from Canada the agent gave my friend shit because she didn't have a physical receipt for the purchase she made and couldn't prove it was worth less than the threshold. Even though I live in a border city I rarely cross because the agents are such assholes

If it's under a certain dollar amount and not to be sold, sure, but this is probably not going to practical for a lot of things unless you're pretty close to the border.
- “Oh yes, officer! This is my washer and dryer from home… I just felt like they needed a bit of fresh air!”

No because once outside of the US people realise the country is shit and they don't want to come back anymore, so this will not work sadly enough.
- Well you see, the problem is, you can just say "I want to leave" and go wherever you want. You need visas.
  A work visa is only temporary and you get kicked out as soon as you get fired.
  So only immigration visas are viable for long term emmigration. Those are very hard to get.
  If you go without permission, you will get deported back to the US.

Welcome to Europe's cheat code. Within an hour I can reach 4 countries with 4 different tax laws.
- Ok, but ir's a cheat code for non-existing problem since non of those countries tax you with addituonal tarifs.
  
  non-existing problem
  It's the other way around: to avoid local taxes on things like fuel, medicine, food, ...
  VAT rates differ between countries, as do the very long lists of exemptions and reductions.
- Lucky you, to get to more than one other country I need at least 3 to 4 hours depending on traffic
  
  From Australia, I'm gonna need a decent boat and a lot of days. Or a plane.

I did that once, when the Nexus phones weren't available in Switzerland but they were in Germany. I ordered it to a location close to the border that specifically offers a postal address as a service and went to pick it up.
The correct thing to do would have been to go to the border agents, get a confirmation that I'm bringing the merchandise out of the country and pay the Swiss VAT. With the confirmation I could theoretically get the VAT back from the seller I paid it to. Except that was Google and they weren't intending to sell it for export, so I doubt they would have helped with that.
What I did was unpack the phone, throw away the packaging, put my old phone in one jeans pocket and my new one in the other, and drive back over the boarder. Having two phones isn't that weird, so I thought I could get away with claiming them as personal items if I was asked. But I wasn't even stopped (they only do sampling at the crossing) so it was easy. But it was technically smuggling. Anything over 300 CHF needs to be declared and VAT paid, the phone was around 400 €.
My mom once went clothes shopping to Austria and didn't declare them. The border guard asked what she bought. She claimed clothes, but not over the limit. He was like no way, I know that brand, they must be worth more, checked the stuff, and discovered it was worth too much. She had to pay VAT plus a pretty decent fine.
I only crossed the US Canadian border once in each direction, but to me it seemed like they were way more strict and thorough than here in Europe within Schengen. So I'd be scared I think. But overall I still think your plan could work if you're careful with it. Maybe gaming laptop would be suspicious if you went for a one day trip, would be better if it was longer. But a phone not really.
- It's been years since I've crossed the Canada/USA border, so things may be different today. But when I went, the Canada side was more concerned about smuggled weapons, while the USA side was more concerned about smuggled drugs. Still, it doesn't take much to trigger a border patrol search.
  Apparently if you go from New Brunswick in the morning, spend the day driving through Maine/New Hampshire/Vermont, and cross into Quebec the next day, that's suspicious enough to get detained for several hours and to have your entire car searched at the border. To me it just made sense to do a straight line drive through those states, since staying inside Canada between those two points would have been a much longer, more convoluted route. Silly me, being logical about my route without considering how others break international law.

Don’t mind me officer, I am just carrying my personal TV and washing machine with me
- Don't mind me, I'm just carrying my um...
  glances at my stuff
  Personal Portable Gaming Desktop PC, 4K 144hz Monitor, Mechanical Keyboard, Gaming mouse, etc...
  👀
  whispers to border agent Btw, I'm a real gamer 😉
  
  That's easy. Your friends had a LAN party 🤓

For residents of the United States the duty free limit when returning is 800 dollars worth of stuff. I believe that's every thirty days. You usually have to answer whether you exceed this limit in the declaration.
So you just go to Canada, buy the thing, unpack it from the packaging, and pretend like its just personal items. Just like a smartphone.
If tariffs become a big thing, this will definitely happen more, but it will also get a lot more scrutiny from customs as well.
AFIAK, border agents usually don't ask if you bought your phone in the US or from outside, they shouldn't ask about other personal electronics, right?
Stuff that you exported and reimported for personal or business use, but not for resale, is exempt from duty with no dollar limits. If you want documented proof that you are reimporting, you can register the stuff at a customs office in the United States before you leave.
- For residents of the United States the duty free limit when returning is 800 dollars worth of stuff
  Well, they just removed the de mininis rule...
  Stuff that you exported and reimported for personal or business use, but not for resale, is exempt from duty with no dollar limits. If you want documented proof that you are reimporting, you can register the stuff at a customs office in the United States before you leave.
  I'm pretty sure nobody registers their personal smartphone and laptop every time they leave the US for a vacation.
  
  My understanding is that the de minimis tariff treatment for import shipments is different than the duty-free personal exemptions that apply for "accompanied baggage" when re-entering the USA and has the imported items with them.
  Assuming this CBP page is accurate, the $800 exemption is one of three possible exemptions that can still apply. The $1600 exemption only applies when returning with stuff from Guam, American Samoa, or USVI, and the $800 can only be claimed every 30 day. The last resort is the $200 exemption, which is always available, and ostensibly is there to allow Americans living near Canada or Mexico to not have to deal with border taxation just because they had to buy lunch or gasoline during day trips.
  
  I'm pretty sure nobody registers their personal smartphone and laptop every time they leave the US for a vacation.
  I agree with you on this, but CBP is certainly within their legal rights to interrogate you on the origins of your personal electronics, and they can make a determination that your stuff is subject to duty if it's over the limit and they don't believe you are reimporting.

According to the customs and border protection website, there is a max limit of $200 that is free from duty and tax if you've spent at least 48 hours there, and it has to be for personal/household use. There are amount limits on alcohol and tobacco.
But if it's something like a single phone, you pay in cash and open it there and dispose of the packing material. You could get away with violating those restrictions, but at your own risk.
Side-note: The limit is $800 if you go to the Caribbean, and up to $1600 for places like US Virgin Islands
- Why is there any sort of limit at the US Virgin Islands? It's a US territory, you don't even go through customs.
  
  Because its a colony that's not equal.

There is a whole genre of smuggling that is literally just buying a bunch of watches or couple of high-end laptops or something and then throwing them in your suitcase and doing exactly this.
If you’re doing it with single items for personal use is it fine? Probably so, as long as you can avoid being extra stupid about it. Is it a good thing to get in the habit of? Oh mercy no.

So, I live right on the Canadian border. Right there.
If I went over to Canada, somebody gave me a bunch of product for free, then I took that product and gave it to someone else for free, would that be legal? No money was exchanged.
Let's say the product was plushies. A large amount of them. What's the legality of that?
- That's a federal crime. If it's for your personal or household use and under $200 you're fine(unless you're coming from China).
  Doesn't seem like a good time to fuck with border control.
  
  Not saying I'd do it. Just proposing a hypothetical to get answers.
  How is it a federal crime, though? No money was exchanged.

Yes I live near a border and I know lots of people who do this.
- The ones that do it for family and friends get away with it, the ones that get peppy and decide to start flogging groceries, etc on Fb Marketplace get watched. It's really not something you want to try to profit from!!
  
  Like many things they won't bother for occasional personal use, but will come down with the hammer if it turns into a business.

I live a few miles from the border and cross at least weekly. You could generally get away with this for a handful of things, especially if you're smart about it (dispose of all packaging and tags, have an otherwise legit reason for a short visit, etc).
But if they question you, and they determine you're intentionally lying about it, you can expect to pay additional fines and lose several hours of your life.

There's a whole TV show about this:
https://en.m.wikipedia.org/wiki/Border_Security:_Canada%27s_Front_Line

Unless you can fly the Kessel run in twelve parsecs, you should probably leave the smuggling to career criminals.

Borders are patrolled by CBP (customs and border protection). Part of CBPs job is to charge you tarrifs on the stuff you're bringing into the country.
Sometimes I've had to pay import tarrifs many times when crossing back and forth (for the same thing over-and-over). Its best not to cross the border with expensive stuff.
- Sometimes I’ve had to pay import tarrifs many times when crossing back and forth (for the same thing over-and-over). Its best not to cross the border with expensive stuff.
  Bruh, that's is so scummy.

Yes. But only one or two things at a time. It's illegal but like you said if you just say you had it when you entered Canada you'll probably get away with it.
If you come over with 100 laptops in your trunk you will almost certainly be forced to pay import duties on them.
Basically if you're trying to save some money personally yes it's possible. Under a certain dollar amount you can usually even do it legally as long as you don't intend to sell it. But if you're planning on making a business out of doing this and selling it in the US cheap then you're gonna get caught