back door contribution to Roth IRA account 的步驟是不是這樣：
1. 開一個traditional IRA, make after-tax contribution；
2. 立即將traditional IRA裏麵的after-tax contribution轉到Roth IRA 以避免產生盈利需要報稅。
但有一個問題，如果還有其他traditional IRA account，比如rollover IRA account，IRS是不是將所有traditonal IRA accounts放在一起考慮報稅的問題？
chatGPT的回答：
When converting from a Traditional IRA to a Roth IRA, the IRS considers all of your Traditional IRA accounts as one for tax purposes. This means that when calculating the taxable portion of your conversion, the IRS uses the "pro-rata rule" and considers the combined value of all of your Traditional IRA accounts.
The pro-rata rule essentially determines how much of the conversion is taxable, based on the ratio of after-tax contributions (non-deductible contributions) to the total value of all your Traditional IRAs. In other words, if you have multiple Traditional IRAs, they are aggregated when calculating the amount that is subject to tax. The taxable amount is proportional to the pre-tax contributions and growth across all accounts.
For example, if you have one Traditional IRA that you want to convert and other Traditional IRAs with different amounts of pre-tax and after-tax contributions, the calculation for determining what portion of the conversion is taxable will take into account all of these accounts, not just the one you're converting.
If you have a mixture of pre-tax and after-tax contributions across different Traditional IRAs, the tax treatment can be more complex, and it’s important to calculate the taxable portion accurately.
