DTA / DTL? When do they come into play?

Lets say I have $20 in inventory. $5 in revenue is generated with corresponding $10 in COGS. The accounting flow in my mind is $3 decrease in NI on I/S (assuming 40% tax rate). On the B/S, inventory falls by $5 and retained earnings in Equity decreases by $3. Net cash for this period is up $2 (NI down $3, $5 increase in cash from decrease in inventory) and the B/S balances. Is this correct?

What happens then if instead of removing inventory due to revenue being recognized, it is written down by $5 instead? Wouldn't the same logic still follow? Other operating expenses up $5 causes NI to fall by $3 (assuming 40% tax rate). On the B/S, inventory also falls by $5 and retained earnings falls by $3. Net cash for the period is up $2 (NI down $3, $5 increase in cash from the decrease in inventory) and the B/S balances. However, I see that some answers include another asset in the form of a DTA of $2 instead of any changes to cash which makes me confused. What exactly is a Deferred tax asset or liability? If you include the DTA of $2, wouldn't the B/S no longer balance since your cash is up $2 from the fall in NI and corresponding increase due to writing down inventory?