Impairment Reversing on PPE involving government grants

Hello All,

I was wondering if anyone can help me with a query regarding impairment reversing on PPE involving government grants. As you have two options when recognising government grants, treat as deferred income and release to the P/L or reduce the cost of asset.

E.g. Building costs $10m and grant $1m then the initial cost would be $9m.

Reduce cost of asset
If you were to conduct an impairment in one year and then following year you want to reverse it, can you reverse it to the full before the government grant e.g. $10M or would it be restricted to $9M

Thanks