Do you know that you have to keep your source documents for 9 years?

Under the self-assessment system for individual tax, you do not need to submit the relevant receipts or invoices to the tax authorities (IRB) for those relief expenses spent or incurred, but instead just keep those documents to yourself in case you may be selected by IRB for random tax audit or when you need tax clearance from IRB for previous years of assessment.

How long you need to keep those receipts or invoices for tax purposes?
Tax rules require you to keep for 7 years.
 The calculation of the 7 year period begins from the end of the year in which the Income Tax Return Form is filed. Effectively, you need to keep it for 9 years. How to calculate to 9 years? You spent/incurred relief expense in Year 1, submit the Income Tax Return Form by 30 April in Year 2, and then keep the receipts pursuant to tax rules for 7 years. Total number of years is 1+1+7 = 9 years.