It's definitely not Beni Otake - that is a linearlobum type with very narrow, bamboo-like leaves. In fact, the name translates to "red bamboo" :-)

Did you plant the tree or did it spring up on its own? That would make a difference but generally, with very few exceptions, cultivars of Japanese maples are extremely difficult to ID. The differences between individual cultivars can be very slight and even JM authorities are hesitant to assign specific ID's.

I can tell you that based on the current growth habit and the spacing of the branches with respect to trunk diameter, this will grow into a good sized tree, probably 15-20 feet, perhaps more. Looks a bit like a Bloodgood clone/seedling.

It's growing from wild seed or it's one you bought and is currently under your deck?

If it's a cultivar you bought, and you are sure of "Beni" in the title, then I'm not sure. Beni kagami looks similar, but the leaf stalks are red instead of green. I like your tree's green stems!

I did not buy the tree, It was already here when we bought the house last September. The former homeowners had no regard for ultimate size...they spent a lot of $ on things and then put them too close to the house. They have a Hinoki cypress right next to it and a weeping larch about 3 ft away.