If one erred or was forced by circumstance and did not pray Shaharit, one prays the Minha amida twice; if Minha, one prays Arbit twice (even though it is after sunset and a new day). If one erred and didn't pray Arbit, one prays Shaharit twice. The first Amida is counted as the newer prayer, and the second as the תשלומין ("compensation") prayer. If one inverted the order, one has not fulfilled his obligation.
CASES OF ERROR:
If one didn't pray because either (a) he thought there was enough time left to pray, and then later he/she forgot, or (b) one was sleeping and the time of prayer expired---this person can make up the prayer he missed.
CASES OF FORCED BY CIRCUMSTANCE:
If one didn't pray because (a) he thought there was enough time left to pray after he finishes what he was dealing with or (b) one who was busy with a business dealing so that it would not result in a monetary loss---this person is able to makeup the prayer he missed.
(Shulhan Arukh and Halakha Berura, Orah Hayyim Siman 108:1,2,8)
CASES OF ERROR:
If one didn't pray because either (a) he thought there was enough time left to pray, and then later he/she forgot, or (b) one was sleeping and the time of prayer expired---this person can make up the prayer he missed.
CASES OF FORCED BY CIRCUMSTANCE:
If one didn't pray because (a) he thought there was enough time left to pray after he finishes what he was dealing with or (b) one who was busy with a business dealing so that it would not result in a monetary loss---this person is able to makeup the prayer he missed.
(Shulhan Arukh and Halakha Berura, Orah Hayyim Siman 108:1,2,8)