There are different ways of dealing with this.
If you have no income at present, then simply fill it in as it is at present.
The other side will then query it.
A lot depends on whether your income is going to go back to normal after the current lockdown.
Alternatively, write to the other side and ask them whether they want to wait to see how the financial situation changes over the course of the next few weeks, before you submit the form.
Personally, I would be inclined to fill it in exactly as the situation exists today because that is honestly what it is and let them query it and come back with queries and if necessary ask for updated information in a few weeks. You don’t how it’s going to change and although it couldn’t get worse, we don’t know when it’s going to get better.
If I have answered your question for you, at the top of the page, you should see a rating facility. Can you please rate my reply 3 stars or more because that really helps me? Please note you are not rating whether it’s favourable, because sometimes you may not get the answer you want, but basically my knowledge and way of dealing.
The thread does not close and I am happy to answer any questions you may have arising from this.