Your original post was not clear; I thought you want just the opposite.
Actually, I didn't think it would split. In any case, it does that automatically.
As I said, I would add a lot of blank space to the end of the band (just stretch it to take up more space), so it would always not fit with the data and print on the new page in whole. And I would put a note on the previous page, as I said above.
But I don't know what else is in your report, and what else is in the summary band.
If you have actual summary info in that band that you would like to keep on the same page as the data, I would create a group and put that summary info in the group footer instead of summary band, and leave only terms and conditions for the summary band.
Another way there is (but I guess I wouldn't go that route myself) is to calculate how much space your other info would take on the page. It could be done in the calling program. Just factor in, how many records is selected for the invoice cursor, how much space other bands would take, and how long is your Terms and Conditions string. Create some variable, either Logic or Numeric (say, 0 or .F. value for not enough room, 1 or .T. for enough room).
Add some invisible (colorless with no borders) shape right after your data, probably in specially created group footer, I guess. Put there "Print When" condition - print it only if there is not enough space. Make sure the shape is not too big, so it wouldn't be carried over to the next page - play with the size. Also, mark "Remove line if blank" for the shape, so as not to leave the space for the shape when it's not printed. Now, if you have enough room for terms and conditions, the shape wouldn't be there, and Terms would kick in. Otherwise, the shape will create the blank space on the page and push Terms to the next page.
Now, if you make changes to your report, you might want to check if your shape needs resizing, too.