CRA appears to indicate that obtaining a clearance certificate does not relieve an executor of personal liability for estate GST/HST obligations

After noting that:

• s. 267.1(2) generally creates personal liability of a trustee (including the executor of an estate) for the GST/HST obligations resulting from the trustee’s acting as a trustee of the trust (or estate)
• s. 270 provides that a representative such as an executor should not distribute property under the representative's control before obtaining a clearance certificate certifying that all amounts, that are, or can reasonably be expected to become, payable or remittable under Part IX in respect of the reporting period during which the distribution is made, or any previous reporting period, have been paid (or acceptable security therefor provided)
• failure to obtain the certificate renders the representative personally liable for the payment or remittance of those amounts to the extent of the value of the property or money distributed.

CRA stated:

That being said, the fact that a clearance certificate is issued to a representative of an estate, does not free the estate from any outstanding obligations under Part IX and as such, the trustee would still be liable to satisfy these obligations pursuant to subsection 267.1(2).

Neal Armstrong. Summary of 28 February 2019 CBA Roundtable, Q.32 under ETA s. 270(4).