If you wish to dispute the assessment, you must lodge a notice of objection in writing stating precisely the grounds of objection within one month after the issue date of the notice of assessment. If the tax charged is excessive by reason of errors or omissions in the return already submitted, you may apply for revision of assessment within 6 years after the end of the relevant year of assessment or within 6 months after the date on which the relevant notice of assessment was served, whichever is the later. State details of the error or omission and submit sufficient evidence to substantiate the claim.