A caveat (Latin for "let him beware") is a notice filed with the Register by a party in interest (known as a "caveator") for the purpose of preventing the Register from granting Letters. The caveat process may be initiated informally or formally.

An informal caveat is a writing filed with the Register (by letter or by use of the form available at the Register's office) simply requesting that the Register not grant Letters without notifying the caveator in advance (Appendix B, Form No. 5). The filing of an informal caveat has the effect of postponing the grant of Letters. As a matter of practice, the Register will notify a caveator of the filing of a Petition for Grant of Letters, and will advise the caveator that the Register will not postpone the grant of Letters for more than 10 days after the filing of a Petition for Grant of Letters, unless within that 10-day period the caveator files a formal caveat and a bond with the Register. During this 10-day period, the caveator has the opportunity to examine the petition, the Will, and any other papers lodged with the Register, and to determine whether to file a formal caveat and bond. If during this period the caveator decides not to proceed, a letter should be sent to the Register by the caveator or the caveator's attorney withdrawing the informal caveat.