Yeah, actually I created my IRS account this week. It gave a choice of a Mortgage or Home Equity account # in addition to last 5 or 6 digits of a credit card # (I don't remember how many digits) , but mortgage didn't work but a CC did. I didn't notice it saying anything about a "soft pull" and I keep all my reports locked, but I created the account OK and I didn't see anything from my credit report. As I recall you can & download your last 6 years of tax returns. You can create an IRS account here: https://www.irs.gov/payments/view-your-tax-account
I made an account in hopes of getting my stimulus payment by direct deposit. I'm semi retired, took early retirement Soc.Sec. at age 62 and still work part time. I file taxes annually but haven't had any federal tax liability for a couple years, I file to get my AZ state income taxes withheld refunded. When I looked at the PDF of my 2019 tax return filed online with Turbo Tax my bank account info was all "x's" on my federal return while my state return had my bank routing & account #s for direct deposit of my refund. So, I made an estimated payment on my 2020 federal taxes of . . one penny. 
Yes, you can make a payment as low as one cent, and it hit my bank account the next day. So hopefully the IRS figures it out: here's my bank info, waiting eagerly for that stimulus direct deposit. 