The AAT has held that it did not have jurisdiction to review an objection decision of the Commissioner arising in relation to his declining to credit PAYG payments the taxpayer claimed to have been made to the ATO by the taxpayer's employer and, accordingly, has refused the taxpayer's application for an extension of time.
In particular, the AAT held that there is no provision made in Taxation Administration Act 1953 for a review of decisions made by the Commissioner in relation to Running Balance Accounts and the application of payments and credits.
The AAT said at para 49:
" It follows that matters relating to PAYG withholdings and to any credits arising from them are quite separate from an assessment of the sort referred to in s 175A of ITAA36. An assessment of the sort made by the Commissioner and to which Mr Beiruti objected does not permit him to raise matters relating to PAYG withholdings because it ascertains only an entity’s taxable income and tax payable on that taxable income. It does not extend to what is, in effect, an accounting exercise offsetting tax liability determined under the assessment with credits such as those provided by PAYG withholdings. As issues related to PAYG withholdings are not encompassed within the process of the Commissioner’s making an assessment, a person cannot seek to have those issues reviewed by objecting to an assessment. Equally, a reviewable objection decision made following an objection to an assessment cannot raise those issues for review in the Tribunal. Therefore, the Tribunal does not have power to review them."
Beiruti and FCT  AATA 634 (5 September 2013)