No, if clients do not have a T1036 completed and filed, they cannot claim that they have made a withdrawal under the Home Buyers' Plan (HBP), even if they have a T4RSP slip showing a withdrawal from their Registered Retirement Savings Plan (RRSP).

The T1036 is the form that must be completed and filed with the Canada Revenue Agency (CRA) to participate in the HBP. This form allows individuals to withdraw funds from their RRSP without incurring taxes to purchase or build a qualified home, subject to certain conditions and limitations.

If clients have made a withdrawal from their RRSP and have not completed and filed a T1036, the withdrawal will be subject to withholding taxes and included in their taxable income for the year. The amount of tax withheld will depend on the amount of the withdrawal and the province of residence.

If clients believe they qualify for the HBP and want to take advantage of it, they must complete and file the T1036 form with the CRA before making a withdrawal from their RRSP under the HBP rules. It's important to note that the HBP rules are complex, and it may be beneficial to seek professional advice from a tax expert or financial advisor before making any withdrawals from an RRSP under the HBP.