Your answer is found in UCC 4-215

The provisional credit is final when the drawee bank honors the item, or the provisional credit is revoked when the drawee bank dishonors the item. Which, again brings us back to the issue of an item lost in transit.
If it takes 6 months for a check to be properly routed to the drawee bank for payment, the provisional credit to the depository bank will be six months.
The only statutory timeframe the UCC provides governing this process is that the drawee bank has until midnight the business day after it receives the check to pay or return it. This is found in UCC 4-302

Quite a learning experience. Thank you very much for helping.
If the drawee bank misses that midnight deadline what would be the consequences?
Are those dates and #s on the back of the check a time table of where and when the check was processed? or how do we know when a bank receives a check?
I asked about this "Late return"(I assume only relates to the drawee bank) previously from my bank and got no where.
Thanks again

What if my bank pays a check and then returns it 2 weeks later unpaid? How can this happen? I had the money in the account the day they paid the check.

How can my bank return a check on my account that they paid on the 2nd of the month and then returned that same check on the 19th of that month?

If the drawee bank misses the midnight deadline (and yes, the back of the check would be very important in proving your case,), and you can prove that you suffered a loss as a result of their violation of the UCC, you may be entitled to damages up to the amount of your loss. If they returned the item late, don't expect them to own up to it and hand over the money, you will probably need an attorney.

2nd anon. based on your description, you bank may be trying to cover an overdraft, and going back two weeks is outside the bounds of the UCC as they are clearly outside the midnight deadline. You are covered by UCC 4-402 which covers "wrongful dishonor"
Your best option is to speak to a manager so they can tell you how what they did is legal. Hopefully they will acknowledge that they should not have done what they did. Also bring in any "returned check fees" you may have incurred from third parties as the statute does provide for damages caused by the dishonor.

Once the dust clears, if paying these items will leave you overdrawn, you will still be responsible to your bank for paying it back.

If your bank refuses to work with you, and the loss is significant enough for you to want to press the issue, again you may need the help of an attorney. Also, you as a consumer always have the right to voice your displeasure by moving your business elsewhere.