Your IVA was proposed and accepted at 60 months. In the 54th month you have to get a valuation of your property. If there is any equity in the property (usually greater than £5000) then you will normally have to do one of two things:
1) Re-mortgage to free up the equity to bring it into the IVA
or
2) extend the IVA by 12 months in lieu of being able to remortgage
Most people can't remortgage so the second option is taken. There are also some caveats around the remortgage regarding how much it can increase your costs by etc etc but if it's not an option anyway then that is moot.
Have you yourself had the property valued, and if so, by more than one estate agent? Some IVA companies seem to be doing 'drive-by' valuations (also known as 'looking on Zoopla') and coming up with a figure themselves. Clearly it's to their advantage if the figure requires more money. For what it's worth, Zoopla appears to over-value my property by some 15-20% so it's worth getting local experts to give you a 'forced sale' value. Get it in writing and take the average value.
The other consideration is whether the property is jointly owned and whether you and a partner are both in a joint IVA? If you alone are in the IVA and the property is owned 50/50 then you will only need to consider 50% of the equity (you cannot be asked to pay in equity which does not belong to you).
For example, let's say your property is worth £200k and is jointly owned. You have a mortgage of £150,000 outstanding on it. The figure used will normally be 85% of the value (so 85% of £200,000) so in this example £170,000. The total equity available is £20,000. As you own half the property, your share is £10,000 and would need to be made available to the IVA. If you're not able to remortgage, you would have to extend by 12 months.
Let's say your property is worth £170,000, jointly owned and with £150,000 mortgage. 85% of £170,000 = £144,500. Mortgage is £150,000 so therefore zero equity and also no extension of the IVA.
This is why it's important that your property is accurately valued, and normally this is the responsibility of the debtor in the IVA.
Check the terms of your IVA and speak to your IP to clarify. If you've not had the property valued yourself I would get this done immediately and remember to ask for a 'forced sale' valuation.
Hope this helps.