Meis accounting entry

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MEIS credit scrip useable (current asset) Dr. To MEIS credit scrip received (indirect income) At the time of import Custom duty dr. To MEIS credit scrip useable at the time of sale of MEIS credit scrip Bank dr. To MEIS credit scrip Debit or credit p & l for profit and loss on sale as the case may be

When should we recognize the revenue, at the time of export or at the time when the scriptt are credited by the government?