If I paid a company in error, and they cashed the check before I could stop payment. How do I go about getting it back? I sent a letter notifying them it was sent in error & that they should return it. As of (over 3 weeks) they have not refunded the money. I owe the $ to another company so truly need it back

Do you owe this other company money? If so... no way are you every getting it back.

Sounds really odd they would cash it without an account to credit it against? Pay the company you DO owe money to... first... you may not get this money back for a month or two. What you can do depends on where they are located and where you are located. You have to sue them on their turf in small claims court... if they aren't a local company that may cost you more than the amount of the funds.

Please define what you mean by "in error". Did you not owe them any money? How big is this company? The bigger they are the more bureaucracy you have to sift through to get a refund. If all you have done is sent one letter, then you need to get on the phone and find out what is happening.

You may have to sue them for the refund if you did not actually owe them money.

If this is a large company, and you owe other money, like a balance but monthly payments, that payment will just be credited to your account.

If you do not owe them money, It will show up as a credit balance, in next month statement and at that point you can request a refund.

Again, please explain the "error" do you owe this company money? Making payments?

But even with a small company, They would have to wait and be sure your check is clearing, (if paid for check) and perhaps have rules for refunds.

Please define what you mean by "in error". Did you not owe them any money? How big is this company? The bigger they are the more bureaucracy you have to sift through to get a refund. If all you have done is sent one letter, then you need to get on the phone and find out what is happening.

You may have to sue them for the refund if you did not actually owe them money.
I did not owe them money, they did not provide me with any service. It was an error on my part when paying via on line banking. My bank paid who I said to, so not their fault. I have not done business with the company in a long while, nor will I be doing business with them again. Especially being they kept the money! I was told by my bank today, that I could have a case against them as they took money & did not provide a service.

Have you called them? Again how large are they? Has your bank requested return of the funds? Have you called them?

You will have to call them and write them. And as noted, yes you will have a suit, but it may be an issue that it will take 30 to 60 days for the accounting to process and refunds to be issues.

A large company, will find your over payment or incorrect payment to an old account number on the next billing cycle, at that point they would have a statement showing an over balance and could issue a refund perhaps on the next billing cycle.

Knowing what type of place was paid, the size of the company, the type of account you had, how long it was since you had an account there.
You are barely giving information, The first step of any, will be a letter requesting a refund, followed by calling customer service

And none of that will happen overnight. Meaning it will take time.

I'm curious. How does one accidentally send money to a business they have done no business with and owes no money to? An envelope has to be addressed to them and check filled out and mailed... all of which requires a specific action. Example, sending a check to Ishmael's Widgets required writing one to them and addressing an envelope to them. The wrong check and bill to the wrong place with pre-addressed envelopes I can understand, but you have business with them. I think there is some important information missing.