When an invitation says only "smart casual", I read it approximately eleven times (the font, the hour, whether the host used a full stop). Then I text a friend, open the closet, and close the closet. I have no shame about this.

 

But somewhere between the office going soft, the weekend getting sharp and every birthday dinner acquiring a dress code, smart casual attire has gotten a little exhausting. We are told casual means comfortable and also that smart means polished. We are told to dress for ourselves and also for the room. The verdict, as far as I can tell, is wear something nice and do not make it weird. If you want to keep going, casual chic dress code is the one I would read next.

 

Which brings me to Debrett's, the British etiquette authority, which calls this "the most ambiguous of dress codes" (its words, and I felt seen). Its reading is kind, though: in essence it is a plea from a host asking guests not to turn up in trainers, jogging pants, sweatshirts, hoodies or beachwear. Most people typing what is smart casual dress code into a search bar want exactly that, permission to stop spiraling.

 

Some of this advice made me feel relieved. Some of it made me suspicious of my own sweaters. And some of it, frankly, made me want to lie down. So, here are five lessons in the smart casual dress code, each one a thing I would actually do, with a few pieces I would reach for in every case. I went deeper on a related idea in The Dressy Casual Edit: Five Lessons for the Dress Code Nobody Can Define.

Smart casual attire is not a uniform, it is a single decision: something in the outfit has a shape. Debrett's calls a smart day dress worn with a jacket a safe choice for women, and the jacket is the part doing the work. Everything else can relax around it. Indeed's career advice, for what it is worth, puts it neatly: smart casual is "slightly less formal than business casual" but still asks for a clean, professional look.

 

The blazer is where I would put the effort. Stella McCartney's oversized beige wool-twill double-breasted is the soft one, and her dark brown wool-flannel version is the sharper cousin. McQueen's black crepe blazer is the quiet one that disappears into a room, which is sometimes the goal. For pattern, Chloé's brown checked double-breasted and its cape-detailed Prince of Wales sibling are both lovely, and Saint Laurent's Prince of Wales check is the most serious of the three. Max Mara's Mirra flannel blazer sits in the middle.

 

The test is simple: put the jacket on over the plainest thing you own, then look in a mirror from the side. If the shoulder line looks deliberate, you are done.

 

What I would skip: a blazer you have to hold closed all night. Although Toteme's black cotton-twill jacket, which is cut more like a jacket than a blazer, is the exception that makes my argument slightly messy.

Debrett's is firm about jeans: choose a clean, dark, well-fitting pair, "rather than a baggy, faded pair with holes and frayed hems". For women's formal smart casual, it adds that denim should be immaculate and balanced with a tailored jacket and smart accessories. I read that as a contract. Dark denim is allowed, and it must be paired with some effort elsewhere. This is the smart casual dress code women ask about most, and the answer is a yes with homework.

 

Saint Laurent's high-rise wide-leg jeans and the Calvin Klein Collection straight-leg pair are the most trouser-like, which is the point. Khaite's Conforti bootcut gives you a longer line, and Nili Lotan's Shon barrel-leg jeans are the one I would wear when the invitation is closer to a Sunday lunch than a Thursday dinner.

 

If the room feels more formal, skip denim and reach for trousers. Saint Laurent's pleated pinstriped wool pair, Dries Van Noten's pinstriped crepe wide-leg pants and Brunello Cucinelli's navy pleated pinstripe wide-leg pants all say suit without the suit. Nili Lotan's gray Etoile pants are the quiet ones.

 

What I would skip: any jean with a visible fade at the thigh. Although a pinstripe next to a dark wash, in the same outfit, is a pairing I would try at least once.

Debrett's has a trick for the moment you feel overdressed: put on a cardigan instead of a tailored jacket. I would take that one step further. A knit with some structure can stand in for the blazer from the start, and smart casual is generally forgiving about it. I also put together The Casual Outfits Edit: Five Lessons in Getting Dressed on a Tuesday.

 

Picture her in a polo sweater, buttoned all the way up, with trousers that have a crease. The polo sweaters here are the secret weapon: the &Daughter Edith in striped wool, the Almada Kaia in black cashmere, Guest In Residence's collegiate striped cashmere and the Faithfull Harlow in navy stripe. Each has a collar, which does the work a lapel would do.

 

The cardigans are the more relaxed answer. &Daughter's Ada striped cardigan, Lisa Yang's navy ribbed Agata and the ARCH4 tweed cashmere Tulip cardigan all work over a plain top. Allude's rib-trimmed cashmere sweater is the plain-top option, for the days when the cardigan is the outerwear.

 

The test is the shoulder: hold the piece up by the seams, and if it hangs in a clean line rather than collapsing, it can stand in for a blazer.

 

What I would skip: anything with a stretched neckline or pilled elbows. Although a well-worn cardigan on the right person has a certain authority.

Every dress code I have ever feared has been solved at the feet, and what is smart casual attire for shoes has a short answer. Debrett's rules out trainers and sandals in smart casual, and a loafer is the shoe that answers both without trying. The best-known one is Gucci's horsebit, which dates to 1953, when Aldo Gucci added a metal snaffle bit across the vamp of a leather loafer, a nod to a horse's bridle. GQ notes that it is now in the permanent collection at The Met.

 

That makes Gucci's Rhody Horsebit-detailed suede loafer the obvious start. Loewe's Double L suede loafer is the quieter option, Zimmermann's cream Astor is the lightest, and Jamie Haller's Penny in dark green calf hair is the one for people who like to be noticed from the shoes up.

 

If you would rather be in a heel, keep it low. Etiquette expert William Hanson advises that heels should not be above three inches, and the pumps here keep well to that spirit: Gianvito Rossi's New Piper 45 in black suede, Nodaleto's Dona 50, Le Monde Beryl's croc-effect Babouche 40 and Khaite's Valerie 55 in calf hair.

 

What I would skip: a stiletto at a lunch. Although I have seen it work and I would never tell anyone otherwise.

The venue is not the person who invited you. Debrett's says that if you are confused by a dress code, you should consult fellow guests or ask the host for clarification, because "at least it shows that you care". It also says it is always more polite to the host to dress up. Town events tend to be more formal than country ones, and a traditional host usually means a more formal style.

 

That is why the finishing pieces matter. A structured bag says you thought about it. Jil Sander's burgundy Kante, The Row's black Alma, Chloé's suede Paddington and Gucci's Jackie 1961 in camel are the four I would choose from, depending on the host.

 

Jewelry should do less. William Hanson's guidance is that it should be modest and nothing showy. Marie Lichtenberg's Clover Baby single hoop, Martha Calvo's double hoops, Sophie Bille Brahe's Lou Esemble pearl necklace and Sophie Buhai's reversible earrings all fit that brief, with the Buhai pair the boldest of them.

 

The test: text the host. One line. It takes eleven seconds, and it is the only reliable answer to the question of what smart casual means at their table.

 

What I would skip: the statement necklace and the statement bag together. Although the host will notice either one.

What these five lessons add up to is smaller than I expected. One piece with a shape, denim that behaves, a knit that holds up, a shoe that closes the case, and a little thought for the person who asked you.

 

I will still read the invitation eleven times. I will still stand in front of an open closet. But I have noticed that the host is almost never checking whether I got the dress code right. They are checking whether I came.

 

So wear the blazer. Or the polo sweater. Either way, call it smart casual and go.