Just be honest and explain why. Just make sure you have a strong or reasonable explanation as to why (example: you're new to your job, you are just newly registered to BIR, etc.). But if you're nervous about not being able to submit an ITR or if you're unsure if your reason is enough, you can then choose to take on a guarantor/sponsor for your Japan Visa application. . However, if you're a self-employed individual or freelancer who works in the Philippines, it is your obligation to register yourself with BIR to get ITR forms later on. For this, I suggest registering with Taxumo because they can take care of literally everything for you: tax forms, payments, and submissions. I've been using them for years now and it has been such a time-saver. Come sign up with my code AILEEN and you can get a 10% discount on all their service plans!