Non-exclusivity of source-based tax collection allows authorities to pursue additional recovery methods when payments are provisional.
Clause 390(4) states that taxes paid by deduction or collection at source, advance payments and specified payments operate in addition to any other mode of tax collection to discharge the liability for income assessed for a tax year, preserving the tax authority's power to pursue alternative recovery measures where such anticipatory payments are provisional, insufficient, or incorrect while allowing credit or refund for any excess.

Tax credit for source deductions ensures remitted taxes are treated as payment on behalf of the relevant taxpayer and allocated by rule.
Clause 390(5) treats sums remitted as tax paid on behalf of the person from or in respect of whose income such tax was deducted or collected, and Clause 390(6) empowers the Board to make rules for allocating that credit to such persons or to others and for specifying the tax year for which credit is allowed, extending the scope beyond conventional TDS/TCS to include specified pre-payments and leaving operational detail to subordinate rules.

Tax Collection at Source: payment obligations arise with income receipt and stand independent of later assessments.
Clause 390 mandates three modes of tax payment-deduction or collection at source, advance payment, and payment under section 392(2)(a)-to be effected "as per this Chapter," establishes that these obligations arise irrespective of later assessment proceedings, and includes a savings provision preserving the substantive charge to tax under section 4(1), thereby ensuring collection mechanisms do not affect the underlying tax liability.