What you describe is indeed latency. However, if you are simply recording guitar or bass there should be none .. unless you are playing through an effect in the computer.
Otherwise it sounds like there may be something set wrong for your input/output drivers.

Are you using the Tascam for both input and output? Realtime monitoring should be available inside the unit thus avoiding any latency at all. (isn't it?)

I do not work here, but the benefits are still awesome
Make your sound your own!