Can a customer who buys from a taxable person who is under composition scheme claim composition tax as input credit

No, the recipient is not eligible to take input tax credit of composition tax paid. Moreover, a taxable person paying taxes under composition scheme is not entitled to collect taxes from the recipient in terms of Section 10(4) of the CGST Act, 2017. Accordingly, there does not arise a question for the recipient to claim input tax credit.

(ICAI FAQ PUBLICATIONS 06-09-2017 COMPOSITION LEVY: FAQ NO. 58)