There are a large number of yellow flowered plants about at this time of year, so any answer wouldn't be an answer it'd just be a guess or a stab in the dark - please post a photo.

Now without a photo, I'm afraid.

Just had an idea - could it have come through from next door? If so it might just be a Kerria japonica. Just google it and see it it is.
PS just noticed that the question below this one is about kerria - what a coincidence - that's weird.

could be a double daisy type helenium/helianthus but we do need a photo.