The "safest" way to ensure that you are opting in to 8% properly, we recommend you do the following:
Make sure you select the correct Taxpayer Type and Income Tax Rate Type:
2. Make sure you select 2551Q and 1701Q in the Forms You are Filing Section:
3. Make sure you FILE 2551Q for the first quarter (either it's Q1 or the very quarter you have to file for aka the quarter you got registered). Taxumo will create a zero due tax filing for you as long as you've chosen 8%. If you missed filing your 2551Q, you SHOULD still be able to opt in by filing your 1701Q on time (best to check with your RDO). If you missed both, then you're no longer eligible for 8%, you'll have to indicate that you're using the Graduated Income Tax Rate.
4. Afterwards, you'll file normally. Which means filing your 1701Qs when they're due. Taxumo will choose the proper option to indicate your 8% opt in.
And that's it!
Why do we recommend that you file a 2551Q?
The challenge here is that there is confusion about the implementation of 8% across different RDO. As we all know, confusion is where the "worms" start coming out and eating at our wallet. So by filing a 2551Q, you avoid having an open case tagged against you -- this is the safest/surest way to ensure maximum protection against said "worms." :)