A Codicil to a Last Will and Testament is a legal document used to amend, supplement, or partially revoke specific provisions of an existing Will without replacing the entire document. The word "codicil" derives from the Latin "codicillus" (a small writing tablet) and has been recognized in Canadian estate law since the earliest provincial Wills legislation. Under Canadian law, a Codicil is a testamentary document that must be executed with the same formalities as a Will: it must be in writing, signed by the Testator (the person who made the original Will), and attested by two adult witnesses who sign in the Testator’s presence and in each other’s presence.

Each Canadian province and territory has its own Wills Act or equivalent statute governing the formal requirements for both Wills and Codicils. In Ontario, the Succession Law Reform Act (R.S.O. 1990, c. S.26) sets out the requirements in sections 3 through 7. Section 4 requires two witnesses, and section 12 voids any gift to a witness or the witness’s spouse (while preserving the validity of the Codicil itself). British Columbia’s Wills, Estates and Succession Act (S.B.C. 2009, c. 13, "WESA") sections 37 and 43 contain equivalent provisions, with the addition of a curative provision (s. 58) that allows courts to validate documents that do not strictly comply with formal requirements. Alberta’s Wills and Succession Act (S.A. 2010, c. W-12.2) section 14 requires two witnesses and also includes a dispensing power.

A Codicil does not replace the original Will. Instead, it is read together with the Will, and the combined documents form the Testator’s complete testamentary instructions. When the original Will is submitted for probate, all Codicils must be submitted with it. In Ontario, the Estate Trustee must provide an Affidavit of Condition of Will or Codicil (Form 74.10) under the Rules of Civil Procedure, confirming the physical condition and integrity of each testamentary document.

A Codicil is needed whenever you want to make a specific, limited change to your existing Will without going through the process of drafting and executing an entirely new Will. The most common reasons for a Codicil include changing the Executor or Estate Trustee (for example, if the named executor has died, become incapacitated, moved away, or if the relationship has deteriorated), updating the testamentary guardian for minor children (under the Children’s Law Reform Act, R.S.O. 1990, c. C.12, s. 61 in Ontario), adding or revoking specific bequests (for example, gifting a new asset or removing a bequest to a person who has predeceased you), and adjusting the residuary estate distribution percentages.

A Codicil is also appropriate when life circumstances change in a limited way: a new grandchild is born and you want to add a specific bequest, you acquire a valuable asset (such as real property or a registered investment) that you want to designate to a particular beneficiary, or you want to add a charitable bequest to an organization like the Canadian Red Cross, Heart and Stroke Foundation, or a local hospital foundation. In Ontario, charitable bequests can generate a charitable donation tax credit under ITA s. 118.1 on the deceased’s terminal T1 return, which can reduce the estate’s tax liability.

However, a Codicil is NOT recommended for extensive or fundamental changes. Estate lawyers in Canada generally advise that if you are changing more than two or three provisions, or if the changes involve complex restructuring (such as adding a testamentary trust, changing the distribution scheme entirely, or addressing a new marriage or divorce), you should revoke your existing Will and create a new one. Multiple codicils create complexity, increase the risk of inconsistencies, and can make probate more expensive and time-consuming. In Ontario, the Estate Administration Tax is calculated on the total value of the estate and is not affected by the number of testamentary documents, but legal fees for probate may increase with complexity.

A legally effective Canadian Codicil must include several essential elements. First, a clear identification of the Testator by full legal name and address, along with a declaration that the Testator has testamentary capacity (sound mind and memory, free from undue influence). Second, a precise reference to the original Will being amended, including the date of the original Will and the codicil number (first, second, etc.). This prevents confusion if there are multiple testamentary documents.

Third, the specific amendments must be clearly stated. Each change should reference the original provision being modified (by clause number or description) and set out the new provision in full. Common amendment types include: executor or estate trustee replacement (identifying both the person being removed and the new appointee by full legal name and address), guardian changes for minor children, addition or revocation of specific bequests (identifying the property and the beneficiary), and changes to residuary estate distribution. The Codicil should be drafted so that there is no ambiguity about which provisions of the original Will are being changed.

Fourth, a confirmation and republication clause is essential. This clause states that the Testator confirms and republishes the original Will in all respects not expressly amended by the Codicil, ensuring that unchanged provisions remain in full force and effect. Fifth, the attestation clause must comply with the witness requirements of the applicable provincial Wills Act: two adult witnesses who sign in the Testator’s presence and in each other’s presence. The witnesses must not be beneficiaries or spouses of beneficiaries (SLRA s. 12, WESA s. 43). Ontario’s 2020 amendments to the SLRA also permit virtual witnessing via audio-visual technology, provided at least one witness is a Law Society of Ontario licensee. Finally, the Codicil should specify the governing province and include a clear execution date.