I can't search for "tax software". Is there a way to change that?

Try

tax* software

thanks

On a related question, if your search word only has 2 letters, can you use double '*' to pad it to 4 letters?

Nope, it will only read one * so you still get the under 4 character length error.

Ok. So this means that the search engine can be fooled into accepting a 3 letter word by adding a '*' at the end, but it won't accept 1 or 2 letter words. Right?