So that or in order that?

We use so that and in order that to talk about purpose. We often use them with modal verbs (can, would, will, etc.). So that is far more common than in order that, and in order that is more formal:

I'll go by car so that I can take more luggage.
We left a message with his neighbour so that he would know we'd called.
[on a website] In order that you can sign the form, please print it out and mail it to this address.

We often leave out that after so in informal situations:

I've made some sandwiches so (that) we can have a snack on the way.

When referring to the future, we can use the present simple or will/'ll after so that. We usually use the present simple after in order that to talk about the future:

I'll post the CD today so that you get it by the weekend. (or ... so that you will get it ...)
We will send you a reminder in order that you arrive on time for your appointment. (or ... so that you arrive on time ... or ... so that you'll arrive on time ...)

So that (but not in order that) can also mean 'with the result that':

The birds return every year around March, so that April is a good time to see them.