Hey, I was wondering how different balance sheet items are written off and/or expensed on the income statement, like reduction of accounts receivable, obsolete inventory, written-down assets, increase in liabilities. Accounting books never actually show where these are written off from, i.e. Revenue, COGS, SG&A, Other.

If you could list where uncollected A/R, inventory write-downs, liability increases and other transactions are written off from on the IS, it would be helpful

Thanks for the help.

It works this way, all writeoffs are a reduction in profit therefore an expense. Whether the item is abnormal or extraordinary depends on circumstance and value.
an Inventory writedown might be accounted for in a number of ways for example;
the COGS might be adjusted by including only inventory on hand and at market value
There might be an account called inventory shrinkage, there might be a provision for inventory revaluation
An asset writedown might be accomplished by adjusting the depreciation rate or charging an account called assets scrapped or bad and doubtful debts in the case of uncollectables
Liability increases are accounted for creating provisions and charging expense as in legal damages, warranty claims

You need to become both creative in your thinking and flexible in your approach because you will encounter many changes from year to year