Yes; that is correct. We did not get a letter from the canton to file the tax return. Since we invested in Pillar 3a and had other deductions for travel and medical costs, we wanted to file the tax return as we would be eligible for a refund of the taxes paid. So, we filed the source tax correction on the recommendation of the tax consultant that we spoke to.

We did receive a refund from BL (only a third of what we were expecting as they considered only a third of the year for the calculation).

I am actually not happy with the tax consultant. He should have advised us to file the source tax correction in BS as well.

Thank you Mullhollander and aSwissInTheUS; this is helpful. We will now file a source tax correction in BS and see how that goes.