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HMRC internal manual

Aggregates Levy Guidance

Unjust enrichment: Extensions to the 90 day time limit

We consider 90 days to be a reasonable time for businesses to pass refunds to customers, and would normally expect businesses to have their arrangements ready to put into action by the time we receive their signed undertaking.

In certain cases it may not be possible to make the refund in 90 days because, at first, the business wrote to customers to see whether their address was correct. If 90 days is not long enough to refund all the money and you are satisfied that genuine efforts are being made to reimburse (repay) customers, i.e. many have already received their money, then you can exercise your discretion and allow a slightly longer period, perhaps 1 month. However, no open ended extension should be given. If after the extension the business has failed to locate the final customers, we should take it that they are not interested in getting a refund.