Tax Paying Form BIR51/BIR52: Using the same envelope to send correspondence for enquiries/claims and the tax return

The question is : Can you send correspondence for enquiries and tax return in the same envelope?

No. Letters of enquiries/claims should not be sent together with the tax return unless it is an objection against an estimated assessment made in the absence of the tax return. Do not staple these letters to returns or bury them among financial statements or schedules.