The disallowance scheme of section 40 come into effect as soon as there is any instance of default in deduction of tax. In  19 ITR-OL 18 (Mad) reasons
were recorded for case reopening stating that the assessee had deducted less tax from the payment to the non-residents, and proportional disallowance under section 40(a)(ia) was therefore called for which was left out in original assessment.
In this case the AO culled/traced out instances of lower than required TDS deduction out of the materials submitted by the assessee during the original assessment and such issue was not adjudicated by the assessing authority then.
Approving reopening action the High Court held that the AO may not have considered all the intricacies involved in business or other transactions. The business and trading activities are being carried out in a calculated manner by the traders. The intricacies involved may be traced out even at later point of time.
This is like you gather books and ledgers besides details information nd scrutinise them later in time nd use the same for reopening. This is perhaps not what is visualised under the law as it would narrow down the functional role of assessing authority.
To hold that the information gathered during assessment but not used may form new material or information for reopening may be kind of overreaching the subject and may be deliberated by the elite class of legal experts before it becomes a practice