For receipt upload, you need to claim the offer first, then you have 4 hours to make your purchase after claiming the offer. After 4 hours, the offer you claimed expires and is no longer valid. If you are required to send a picture of your receipt in the app, you have 24 hours to upload the image you took of the receipt. You'll be notified when the offer has been processed.
For Check In offers, click here.
It's a lot of numbers, but when done correctly, they all add up to your cash back!