This part of GOV.UK is being rebuilt – find out what beta means

HMRC internal manual

Aggregates Levy Guidance

Errors and Assessments: Central assessments

If no return is received by the due date, Central Collection Unit (CCU) in Southend send the business a central assessment. These assessments are sent one week (5 working days) after the latest date on which a return should be made.

Where… the amount of tax assessed is based on…  
no returns have been made, the estimated taxable tonnage given by the business on their application to register.  
returns have been made, the preceding returns.  
the second and subsequent returns have not been made in any 12 month period, an inflation by 25% each time.  

Where a central assessment is issued (by virtue of Finance Act 2001 Schedule 5 para 2), and during a visit it is found that the business did not subsequently make a return and that the central assessment is not correct, the business should be encouraged to send a return and any net payment due. If the business indicates it is unwilling to make a return, or subsequently fails to do so a further (officer’s) assessment can be issued under Schedule 5 para 3.

An inaccuracy penalty may also apply when a business has not notified us the central assessment is too low.