Reimbursements Received and Owed (not mileage/medical/childcare-related)

[mohowe]

I am a W2 salaried employee, and have used my own personal money to cover company expenses. Expenses included supplies, equipment, rentals, bills, etc. My company has committed to reimbursing me in full for all expenses.

At year end, I've only received a portion of the money due to me. The reimbursements I've received so far have all been listed as non-taxable line items on my pay checks.

Is there anything specific I need to do for my received and for my outstanding reimbursements?

[Opus 17]

Reimbursements are not taxable if they are made under an "accountable plan" -- you provide receipts and are only reimbursed for actual expenses proved by receipts.  

Expenses that are not reimbursed can be deducted as work related expenses as itemized deductions using form 2106 and schedule A.  But, if you deduct the expenses now and are reimbursed later, the reimbursement will be taxable income for the year you get it, because it is a recovery of a previous tax deduction.  (You can't take a tax deduction and also get reimbursed tax-free.)  So if you expect to eventually reimbursed, the simplest thing to do is leave the expenses out of your tax return.