If IRB wants to make it compulsory for all employers, they should issue the Form E to them and not wait till they come and apply since their system should have all the info
the income tax act is drafted in the way that you are 'guilty unless proven innocent', because you have to pay tax in advance, CP500 & CP204 before you file in your final tax. in 1 way it reduces your burden by not having to pay 1 lump sum which the amount may be substantial but on the other hand, you don't earn interest by depositing to IRB.

1 more thing is, you better don't underestimate because you will be penalised if the difference between estimation and actual is more than 30%.  as if all the business profits can be estimated reliably...

for a well manage business, i feel that the 'paying tax in advance' practice is unfair to the taxpayer

is it advisable to submit our income to gov even earning below 2k?

Paying taxes is normal but paying taxes in advance is not normal. Sometimes you have not even received the money(cash flow) but have to pay in advance first.

6th and 9th revision are still before year end, business carries risks and uncertainties. It may experience fluctuations in final months, therefore the paying in advance practice does not benefit taxpayers. You pay them is easy, there's always e-payment system on irb website but where is e-refund?

Your less than RM30K income per year not subjected to tax is wrong since you assumed that employee has contributed epf, what if he did not and he does not claim other reliefs?

A notice of assessment has not come out but you need to pay first, how can that be fair? Underestimate will subject to penalty but overestimate has no interest, fair? At least our neighbour, Singapore does not practise such tax collection method.

Offset tax instalments is very theoretical but when it comes to practical, it can be very confusing. You may offset current tax instalments with previous overpayments but what if you revise the previous YAs tax comps? The keep tracking procedures are very troublesome especially those clients who do not always pay on time, penalties come in again and make the situation worse. Some of the balances may be from the 90's, able to track?