By Lynne Adkins

PHILADELHIA (CBS) — Buying online at the holidays can save a lot of time and money.  But if you’re not charged sales tax, better save those receipts!

If you would pay sales tax on an item in a brick-and-morter store, Pennsylvania wants you to pay sales tax when you make a purchase online — or report it on your income tax form in April.

Jerry Glynn, managing director of Grant Thornton financial specialists in center city Philadelphia, admits it is an honor system.

“Beginning last year, with the 2011 individual income tax return for Pennsylvania, on form PA-40 they’ve added a line for taxpayers to report and remit Pennsylvania use tax, and that line will continue to appear on tax forms going forward,” he tells KYW Newsradio.

Glynn says that for items under $1,000, you can estimate your total use tax obligation with a table provided by the Commonwealth.  But for that new computer or those diamond earrings, save the receipts and give them to your accountant.

Last year, which was the first year of the reporting, Pennsylvania took in only a few million dollars.