It depends on the lender and the nature of the issue; many lenders will refuse to lend, or require the issue to be resolved first, if there is unauthorised development, an open enforcement notice, or missing retention permission. Some lenders will accept a solicitor's certificate of exemption or evidence of retention permission as a way to proceed.
Mortgage lenders in Ireland rely on their solicitor's report on title, which includes a review of the property's planning history, to satisfy themselves that the security they are lending against is legally sound and unaffected by unresolved planning risk. If the solicitor identifies unauthorised development, such as an extension without permission, exceedance of exempted development limits, or an open enforcement notice, the lender will typically require this to be resolved before releasing funds, since an unauthorised structure can affect the property's value and marketability.
In many cases, the issue can be addressed through a solicitor's Certificate of Exemption, confirming that particular works are exempted development and did not need permission, supported by an engineer's or architect's report on dimensions and compliance with the relevant limits under the Planning and Development Regulations 2001. Where works are not exempt and require permission that was never obtained, the lender will usually require retention permission to be granted and, in some cases, for any enforcement action to be resolved, before drawdown.
Requirements vary between lenders and can also depend on the scale of the issue relative to the property's overall value, for example a large unauthorised extension is treated more seriously than a small, later-added shed. Buyers and existing owners refinancing should raise any known planning issue with their solicitor and broker early, since resolving it, whether through documentation, retention, or remedial works, can take weeks or months and affect the transaction timeline.