Speaking with my own accountant over the last few days,she was saying that she's kinda expecting Revenue to offer self employed(they currently don't)the option to "warehouse" their liability for this year,you could always write to them and state your case if you had encountered problems,i'm filing my 2019 returns now and because i pay prelim tax i only owe a relatively small amount(Payable Nov 12th)and have up till Nov 11th to decide whether to pay prelim or enter Nil for 2020.
I'm due to change car next Feb so every cent i can save till then i will,my accountant is aware of this also.