The RCC built their 'purgatory theology' on a passage in which St. Paul told Christians that there would be a judgement, not of them, but of their works. Here is that passage:
By the grace God has given me, I laid a foundation as an expert builder, and someone else is building on it. But each one should be careful how he builds. For no one can lay any foundation other than the one already laid, which is Jesus Christ. If any man builds on this foundation using gold, silver, costly stones, wood, hay or straw, his work will be shown for what it is, because the Day will bring it to light. It will be revealed with fire, and the fire will test the quality of each man's work. If what he has built survives, he will receive his reward. If it is burned up, he will suffer loss; he himself will be saved, but only as one escaping through the flames. (I Corinthians 3:10-15,NIV)
Many protestant denominations agree that there will be a 'Christians Judgement', in which what we have done on behalf of the furtherance of the kingdom of God will be tested. But the test will consist of how diligently we promoted the teaching that there is only one foundation, namely, Jesus Christ himself. Even though we don't agree with the RCC's teaching concerning purgatory, we do agree that there will be an accounting which we as Christians will have to give.