Ontario Landlords: A Complete Guide to the A4 Application for Amending an LTB Application or Notice (2025 Update)

The A4 Application – Application to Amend an Application or Notice allows landlords and tenants in Ontario to correct, modify, or update information on an application or notice that has already been filed with the Landlord and Tenant Board (LTB).

This process is governed by the Residential Tenancies Act, 2006 (RTA) and the LTB Rules of Procedure, which require all amendments to be formally approved when they affect core components of a case.

The A4 is essential when errors, omissions, or new information might affect the validity of an existing LTB application.

When an A4 Application Can Be Filed

An A4 is used when a landlord or tenant needs to amend a notice or application after it has been filed. Common reasons include:

1. Correcting Clerical Errors

Examples:

• Wrong unit number
• Incorrect rent amount
• Incorrect dates
• Misspelled names
• Math errors in arrears calculations

2. Adding Newly Discovered Information

Examples:

• Updated arrears amount
• Additional incidents or evidence
• Clarifying the reason for termination

3. Changing the Relief Sought

For example:

• Adding a monetary claim
• Adjusting rent arrears
• Changing the requested termination date

4. Correcting errors in termination notices

Such as:

• Fixing dates on an N4, N5, N6, N7, N8, N12, or N13
• Updating details that affect the legal validity of the notice

5. Updating an application due to new payments or changes

For example:

• Tenant made partial payments
• Additional months of arrears accumulated
• Agreement terms have changed

The A4 protects both parties by ensuring the case is accurate before the hearing proceeds.

When the A4 Cannot Be Used

The A4 cannot be used for:

• Replacing the entire notice with a substantially different one
• Changing an N12 or N13 in a way that resets timelines
• Adding new grounds for termination not included in the original notice
• Filing a completely different application type
• Correcting fatal defects where the original notice is void

In these situations, the landlord may need to serve a new notice and start over.

What Must Be Included in an A4

A complete A4 application should contain:

1. The Original Application or Notice

Including:

• The LTB file number
• All pages of the original form
• Any supporting documents originally filed

2. A Clear Explanation of the Amendment

The landlord or tenant must explain:

• What is being corrected
• Why the correction is necessary
• How the correction affects the application

3. Supporting Evidence

Examples:

• Updated rent ledger
• Corrected termination notice
• Bank records
• Written communication
• Repair invoices
• Clarification documents

4. Completed A4 Form

With:

• Applicant information
• Case details
• Requested amendments

5. Filing Fee

If required by the LTB at the time of filing.

Serving the A4 Application

Once filed, the applicant must serve the A4 on all other parties, including:

• The tenant (if the landlord filed it)
• The landlord (if the tenant filed it)
• Any added parties (if applicable)

Service must comply with RTA section 191, including:

• Personal service
• Mail or courier
• Email (only with prior written consent)

The applicant must keep proof of service.

How the LTB Handles an A4 Application

1. Review for Completeness

The LTB reviews the A4 to ensure:

• The amendment is allowed
• The change does not prejudice the other party
• The filing meets procedural requirements

2. Possible Hearing

For significant amendments, the LTB may:

• Hold a hearing to determine if the amendment should be permitted
• Assess whether the other party needs more time
• Consider fairness and procedural history

3. Decision

The LTB may:

• Approve the amendment
• Deny the amendment
• Approve with conditions
• Adjourn the matter for further evidence

When approved, the underlying application continues with the corrected information.

Common Mistakes to Avoid

Common errors that cause problems with A4 applications include:

• Trying to use the A4 to introduce entirely new grounds for eviction
• Amending termination notices improperly
• Not serving the A4 application on the other party
• Incomplete or confusing explanations
• Incorrect file numbers or missing attachments
• Using the A4 to fix a notice that is fundamentally invalid

The A4 can fix clerical or informational errors, but it cannot save an application based on a defective or unlawful notice.

When to Seek Professional Assistance

Professional support is often useful when:

• Multiple corrections are needed
• The original notice may be invalid
• Monetary amounts have changed significantly
• The tenant disputes the correction
• Procedural timelines are at risk
• The application involves complex evidence or multiple parties

Properly preparing an A4 increases the likelihood of acceptance and prevents delays.

Sources

1. Residential Tenancies Act, 2006 — Sections 187–191
2. Landlord and Tenant Board — A4 Form
3. LTB Rules of Procedure — Rule 19: Amendments
4. LTB Interpretation Guidelines