You'll need to elaborate.
Which VAT code are you using?
If you're not working with standard/accrual VAT, any scheme?
Go back to the Bill/Expense entries - is the VAT showing as plus/minus on the screen?
What's the VAT code shown on the Bill input screen
There are several Reverse Charge codes @accounts5-dattan that all do subtly different things.
They should all show something like this at the bottom of the Bill input screen though...
VAT @ 20% on 100.00 £20.00
VAT @ -20% on 100.00 -£20.00