On my W2 the amount reported in box 1 is less than the amount reported in boxes 3 and 5 (which are identical). The difference is equal to the amount reported in box 12d. Also, in box 13 the retirement plan box is checked. My question is how and where do I report the amount from box 12d on form 1040.

Thanks,
Roger

You don't report box 12 any where on your incomne tax form. If marked with code D this amount is your 401(k) contributions. Recall that your 401(k) contributons are excluded from federal income tax - and hence not included in the federal wages reported in Box 1. Box 3 and 5 report your income for social security and medicare tax purposes - your 401(k) contributions are NOT subtracted from those numbers, hence the difference.

Thanks