I am not a tax law expert but itnis reasonable to assume they will start digging deeper and deeper.
I recall having to explain a big jump in assets and it was not a big deal - i created a simple brisge explaining equity vesting, bonus payout being invested at market lowpoint with big increase afterwards, etc and they accepted it without further documentation
Be thorough and transparent in your tax return plus good documentation, and my experience is very positive. I’ve made deductions where i no longer had the invoicr yet simply showed the payment from bank plus a written explanation from me what for and they accepted it. Very much trust based.