The IRS sent me a CP2000, which said I didn't file 1099 income for $1300. My client neveer sent me a 1099, how did IRS come up with this amount?

Taxpayers must always remember that employers, financial institutions, and clients file information returns to the IRS in order to substantiate their own tax deductions.

The IRS matches amounts reported on tax returns with the information returns.

This computer matching begins after original return due date.

If the IRS computer does not find that amount on your tax return, it is an "automated underreported" amount.

Where you paid $1300 for work that you completed for your client?

It is best to return to the tax professional who prepared your tax return and explain the facts. If you prepared your own tax return, find an experienced tax professional to make sure the situation is handled correctly.