when you purchase an asset for $1000
you will record on books
assets - credit $1000
cash(equity) - debit $1000
when you receive rebate for $300
asset - debit $300
cash(equity) - credit $300
So for a financial statement - your assets should be $700 - and you are absolutely correct.
For tax calculations - see IRS publication 551 page 5 - http://www.irs.gov/pub/irs-pdf/p551.pdf
The following items reduce the basis of property.
-- Rebates from a manufacturer or seller.
So for tax purposes the basis of the asset for depreciation and for capital gain (if the asset is sold) purposes - is $700
Let me know if you need any help.
Tax Preparer
Personal Investment, Tax Preparation
if you purchase something - that is a debit for your cash account
If you receive the money - as in your situation - the rebate - that is a credit of your cash account.
Your actual transactions for your cash account
debit $1000
credit $300
Total ($700)
If you purchase asset - your asset account is credited , but if you receive a rebate your asset account should be debited
credit $1000
debit $300
Total $700
Your friend is credited asset account when the rebate is received - that is a mistake.