I need a really simple spreadsheet....

[paradigm]

Thanks Paradigm,

Why that does indeed turn everything into a negative, for some bizarre reason, the auto sum still treats it as a positive, so even though I have -£20 in the stakes column and £20 in the returns column, it still sums it at £40 rather than £0.

I've tried ways that I've found online, yet none of them work. I thought this would have been very easy to accomplish.

Leave the stake as positive. Then under cell D2, enter the following formula -

=SUM(-A2+B2)

Exactly. All the - (and the £) does is add a formatting character to what is essentially a raw number. It's decorative only, so the simple solution is, as gillywibble said, to negate the sum rather than add.