1) Is tax deadline 5-17-21 even if I don't owe any taxes but getting a refund? 2) Can I submit payment to my IRA when I file my tax or must be deposited on 5-17-21?

[fanfare]

the custodian must credit your account for the contribution on or before May 17.

go to a branch office in person, with funds, if you don't have an IRA.

Otherwise make a deposit online now.

if you are sure you will get a refund, you can't be late until three years have passed. Then it is too late.

[ToddL99]

The tax filing and payment deadline is May 17, 2021. The deadline to fund your IRA for 2020 is also May 17, 2021 (see @fanfare post immediately above)

Penalties for filing late are based on the tax due - if you are getting a refund, the late-filing penalty is "0".