Yes, an IVA will show on your credit rating. But if you have been missing payments or making repayments which are lower than your original lending terms then your credit rating will already be damaged.
Your IVA will show on your credit file for a total of six years. However, as your IVA will last for 60 months there will only be one year where you may want to borrow and be suffering from a poor credit rating. Once the final 12 months are up then your IVA will be removed.