I am planning to withdraw the full amount of ‘Cost of attendance’
given by school for a semester from 529 plan.
If you are also wanting to clam the American opportunity Credit which is also in pub 970:
Figuring the Credit
The amount of the American opportunity credit (per eligible student)
is the sum of:
100% of the first $2,000 of qualified education expenses you paid for the eligible student, and
25% of the next $2,000 of qualified education expenses you paid for that student.
Then the $2,000 or $4,000 must come from non-529 funds. I am assuming there were no scholarships involved.
This credit means that $2,000 that would have gone to the IRS will instead help pay for college. That was something I wasn't aware of until another parent told me about it.
Note there is also a MAGI limit:
Effect of the Amount of Your Income on the Amount of Your Credit
The amount of your American opportunity credit is phased out
(gradually reduced) if your MAGI is between $80,000 and $90,000
($160,000 and $180,000 if you file a joint return). You can't claim an
American opportunity credit if your MAGI is $90,000 or more ($180,000
or more if you file a joint return).
Yes keep all receipts. This is always good advice regarding taxes. Also keeping those receipts can be a big help when double checking the 1098-T and 1099-Q.