A quick question, do we need to declare the distributions from unit trust in the tax return? In my case, I have dividend vouchers from fundsupermart. The vouchers stated that the income has already been tax deducted.

I think yes, this income is derive in malaysia even is oversea customer.

Advice from non tax agent 

If you have not used it to set off other income like salary or rental in the same year,
any unused business losses will accumulate and be carried forward to later years.

But those unused losses can be used to set off any profit (adjusted, that is)
in future years from that business source only.