Assessment notices are issued when the income tax return has been processed and the resulting tax liability calculated.
If a return is not submitted then a late return penalty will be issued and a default assessment will be calculated based on best judgement and the information contained in previous assessments or information provided by third parties i.e. employers.
Depending on whether you have made payments towards your liability during the tax year, for example, through the ITIP system if you are employed or due to making a payment on account, then you may have a resulting tax charge due or be entitled to a refund.
If you are due a refund then, subject to checks being made, a cheque will be issued to you shortly after the assessment is issued. If you have any other income tax liabilities for the same year or previous years then the refund will be offset against these debts first and any resulting balance refunded by cheque.
If a refund is generated based on a default assessment then the refund will not be issued until the return is submitted and the assessment is recalculated.