You could look at your original loan document. It's a contract. It should be spelled out there. But, yeah, you're right. Interest piles up every day. Not just all at once at the end of the month.
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Here's my own experience: When I paid off my last student loan (Hurray!) I simply wrote a check for the amount owed and sent it by the due date. But perplexingly, a month later I got a letter saying I owed another 8 cents. I laughed and threw it in the trash. I got another letter the next month reminding me about the 8 cents. Again I ignored it, assuming that they would wise up and quit sending me letters. Well, after several months the tone of the letters became increasingly stern. It was really quite humorous. I got to where I actually looked forward to their next threatening letter to me, the scofflaw who owed them 8 cents. Eventually I cut them a check for 25 cents and sent it to them. Then a month letter I typed up a letter saying that I had inadvertently overpaid my account. I demanded that they send me a check for the 17 cents they owed me. I never heard back from them.
You outlaw.
I've got 2 similar stories.
Years ago a big conglomerate who I worked for decided to close several non core businesses, one of the ones I worked for of course. At the time I was sort of pissed. I had been purchasing their stock so I sold all but one share and had them issue me an actual stock certificate for it. This was back in the mid to late 90's. Well, once they issued the stock certificate they had to start sending me quartery dividend checks. That's right, still to this day I get four 25 cent checks per year from them. They have begged me to put the stock in their brokerage account so they can simply reinvest the dividends and quit spending 40 some cents to mail me a check. Nah, I like that supplemental income. Plus as stock holder I get their yearly glitzy corporate report book which has to cost them at least $15 every year. I'm not vindictive..... Did I mention I changed the banner name on my company phone to "Blow Me" before I turned it in?
I also have a customer that consistently pays their bills about 2 months late. They aren't a big customer so it isn't often but they always want lien waivers returned immediately. That's right, I sit on them and mail them back in exactly the amount of days their payment was late. It's the little things....
Little things can give such great pleasure.
However, sometimes they can be big things.
When I lived in Des Moines, I sold products to one of the largest home builders in the city. They would order several times a year and the bill would be $20,000 to 30,000 each time. Well, my terms to them were 15% net 30. So, they get a 15% discount if paid in 30 days. Well, this company would never pay on time. Finally, I got tired of it and one week after they went past 30 days, I would send them a letter saying they are past due and they owed the full amount. That's $3,750 on a $25,000 bill.....several times a year. They would simply turn around and pay the full bill and not even question it.
This business relationship went on for years like this. I learned to love that company.