Vanguard only shows last 7 years of Form 5498. How do I document Roth contributions older than that?

Hi everyone, I’ve been contributing to a Roth IRA at Vanguard for about 10–11 years. When I checked Vanguard’s tax center, I can only download Form 5498 for roughly the last 7 years. Older 5498s are no longer available online. I have saved all my tax returns over the years, but I’m a bit unclear on how this works when it comes time to withdraw Roth contributions. My understanding is that Roth contributions can be withdrawn tax and penalty free at any time, but how do people typically document their total contribution basis if the custodian does not retain Form 5498 indefinitely? Specifically: • Are old tax returns sufficient documentation if ever questioned? • Do IRS transcripts show Roth contribution history reliably for older years? • Is there anything else I should be doing now to make future withdrawals straightforward? I’m not planning to withdraw yet, just trying to make sure I’m properly prepared and keeping the right records. Thanks in advance for any guidance.