HST-exempt business: can I still claim all business expenses if renting out the office part-time? (Rent is HST-taxable)

[just_asking]

In Ontario, psychotherapists became HST-exempt in June 2024. Because I no longer charge HST on my psychotherapy services, I should no longer claim HST on business expenses. Simple enough.

But… I rent out my office, part-time, to another psychotherapist — and that rent is HST-taxable.

I called CRA; they said that I can claim HST credits on business expenses incurred to provide an HST-taxable service. 

If I didn't run a psychotherapy practice, I would have no office to rent out. So, can I still claim all business expenses as before, since they're required to run my practice and maintain an office to rent out part-time? If not, how do I determine which business expenses are eligible for HST credits?

[TurboTax_Susan]

We are not able to give advice on this as we are not tax experts. Also, TurboTax software can't be used to file GST/HST returns, and we only support what's in the software.