Thanks, I think I've got that, but just to be clear, given the formula in the link
Size for spread bets means size of bet
Size × closing price × LIBOR +/- 2.5% ÷ 365
So if I have a spread bet on say the FSTE 100, which had a value of 7500,
If my bet size was 10, and the LIBOR is 2%
If I keep that open past 10pm then my daily interest would be
10 * 7500 x (2 + 2.5) / 365 = £9.25 per day.
OK, got that I think, so what are the %'s listed in https://www.ig.com/uk/help-and-support/spread-betting-and-cfds/fees-and-charges/what-are-igs-shares-spread-bet-product-details
Specifically these ones; which imply you expect some bets to be held for months, but given the daily interest that doesn't seem to be a good strategy?