What is the difference between pay on and pay for?

"To pay on" is very rare. You probably don't need to know it. I'd be more likely to say "to make a payment on." That implies that there's a full amount, and the payment is for part of that amount. For the first sample sentence, I would also likely say "than he is spending on groceries."

“Pay on” isn’t anything special. The modifier “on” is used in its normal way. When you pay *for* something it’s assumed you are paying the whole bill. On is a word of addition, one thing on top of another, which helps us understand that you’re paying a little bit on a little bit, repeatedly. This is much less commonly used in American English but it’s universally understood because it’s a bog standard use of the modifier.

I don't see "pay on" very often and those uses seem really unnatural to me (New England)

When I say I'm paying on something, it usually means I'm making payments on a debt or for something I have contracted to pay in a reoccurring lump sum, like a streaming service, rent, or wi-fi service. When pay to receivesomethingI'mnot contractuallyobligatedto buy (even if I need it) Iuse gor. "I spend $30 on wifi, $2000 on my mortgage, $200 on insurance. I spend about $300 a month for groceries. But when I start talking about whether I'm getting value for my money, or who precisely is doing the pays, switch to for even gor contractual obligations. "I pay you $30 a month for wifi, but it's down one day out of three." " It's your car, but I pay for the insurance, so I should get to drive it." "Let me pay for your Netflix this month." Which sounds precise, but in actual daily usage it isn't. Even the example quoted by the OP isn't. Either a car loan payment, or a car insurance payment would be a reoccurring payment, as would rent, or a lump sum phone bill. But groceries are not that, nor us gas, or auto maintence. But once we start saying either on or for, we tend to be all matchy matchy and stick to our first choice unless we are making a deliberate contrast like this: "I can't change the amount I pay on the mortgage, but I can change how much I pay for groceries." But even then I might use for for both the groceries and the mortgage.

This if a weird turn of the phrase "to pay off" (a debt) Its implied in the description that youre continuously paying for something you make *payments on*, because you still have an outstanding total(debt) Paying something off is differentiated by the fact thats the final bill, with no debt remaining. They have paid off their car once they no longer make monthly payments.

Neither of those examples sound right to me as an English person. The first would either be "He's spending more on his car than on groceries" or "he's paying more for his car than for groceries". As for "paying on a phone bill", I've never heard that phrasing being used. If I owe you money I can "pay up", if I have a loan with the bank I can "pay down" or "pay off" that loan (partial or full repayment) and if I am running a casino I can "pay out" on your winning bet. A bill is either "pay" or "pay for".

This is an unusual and very colloquial form. I don’t think you need to spend much thought on it. You probably won’t encounter it in the wild and you’d like want to use something more standard yourself.

Does that second example sound normal to anyone? I'd just say "paying a phone bill every month".

Phrasal verbs are entirely self-contained. "To grow up" and "to show off" are phrasal verbs. It sounds 100% natural to say "When did you grow up?" or "When did you show off?" "When did you pay on?" doesn't make any sense. The first example sentence sounds natural but the "on" is part of the "on his car..." phrase and not "paying... on" The second example sentence doesn't make sense. I've never heard of anyone "paying on a bill". You "pay a bill" or you could "pay money toward a bill" or "put money toward a bill". You could also "pay the check" or "pay for the check" and "to pay for" is not a phrasal verb either, the "for" is connected to what's being paid.

It's very rare for anyone to say "pay on", but "spend on" is very common. "How much do you spend on your monthly bills?"

"Pay on" is short for "making a payment on (x)". "Pay for" is to outright pay for a service or item. You *pay on* a credit card bill. You *pay for* your groceries. The example they used is rather unusual. You wouldn't say you're making a "payment on" a phone bill, because it's not a debt. Your paying *for* a service. It's a bad example of "pay on". It is not impossible to say it this way, it would just be weird. I don't think I'd say either in this scenario honestly. In most scenarios, pay for is the most appropriate, and in modern speaking, at least where I am from, *on* is completely ommited from the equation. "I'm going to *pay* my credit card bill" is more typical and natural in my opinion.

I don't think that's a trustworthy article. The second sentence is straight-up ungrammatical in any version of English I'm familiar with, and the first sentence is iffy - you can definitely "spend on" but "to pay on" is an unusual construction to my (Northeast US) ears. "I'm spending more on groceries than ever!" OK "I'm paying more for groceries than ever!" OK "I'm paying more on groceries than ever!" NOPE You can "pay for" an item or service, and you can "pay" a bill or a specific amount of money (no preposition). I don't think "pay on" is standard, although except maybe in the context of something like "I'm going to pay more on my student loans each month so I can be done with them sooner."