If it's for working out your IVA proposal to put towards creditors then it's 100% of everything left when your outgoings are deducted from your income.
I think the good thing about a standard IVA proposal is you can usually keep anything over 10% of your monthly income used to write your proposal (so if you do a little overtime you can keep the 1st 10%) then you may be able to keep 50% of anything over 10%.
Annual pay increases are normally treated as 50% due to the IVA pot and 50% retained by yourself.
Of course you need to check your own IVA proposal to make sure this is all captured.
Dear Louise.63,
Please contact me via the email address in my profile so I can take a look into your case and address your concerns.
Speak soon.
Thanks,
Evette Everest