In order to understand what Jehovah’s Witnesses believe with regard to Romans 6:23 and having ones sins blotted out, we first need to go to Romans 6:7 in the New World Translation and tie it in to what they say will happen at the resurrection. The January 2010 Awake magazine had this to say about the subject:
The Bible says that during Judgment Day the dead will “rise up.”... Jesus will bring those asleep in death back to life again on earth. Will the judgment of resurrected ones be based on what they did before their death? No. The Bible teaches that “he who has died has been acquitted from his sin.” (Romans 6:7) So, like those who survive the end of this system, those resurrected to life on earth will be judged “according to their deeds” during Judgment Day. https://www.jw.org/en/library/magazines/g201001/what-is-judgment-day/
According to this, death blots out the sins committed by people when they were alive. Then, when they are resurrected, they will be given earthly bodies and will be judged during the thousand year reign of Jesus Christ and the 144,000. They get a second chance to be saved. The final test comes at the end of the thousand years when Satan is released for a short time. Those who remain faithful and obedient to Jehovah and his people will be rewarded with eternal life on earth. Those who follow Satan will be annihilated. This is confirmed in chapter 7 of their little booklet ‘What Does the Bible Really Teach’ on page 73.
The answer to this question is that Jehovah’s Witnesses believe Romans 6:23 (in conjunction with Romans 6:7) means everyone who is resurrected has had their previous sins ‘acquitted’ and they get 1,000 years grace during the ‘judgment day’ to get right with God. If they fail the final test they will be annihilated.
It would be remiss of me not to show how various Bibles translate Romans 6:7:
Romans 6:7 NWT: For he who has died has been acquitted from his sin
Romans 6:7 KJV: For he that is dead is freed from sin
Romans 6:7 NIV: Anyone who has died has been freed from sin
Romans 6:7 NIV: For one who has died has been set free from sin
Romans 6:7 NLT: For when we died with Christ we were set free from the power of sin