You will use your trade confirmations and statements to report your IRA contributions to the IRS.
You will receive a 5498 if you owned a retirement account (such as your Aspiration IRA, or an external employer-sponsored plan account) and you either made a contribution (including catch-up contributions) to an IRA between January 1st, 2018 and April 15th, 2019 or you completed a rollover into an IRA during this timeframe.
While Aspiration sends a copy of this form to the IRS, it generally isn't necessary when you're preparing your tax returns. All you need to do is keep it for your records!
This form is distributed in May, because contributions can be made until April 15th, 2019 for the previous tax year.