How long does it take to get an IRS refund if you file late?

Obviously this can only be addressed on a generally basis, many factors - how well the return is prepared, how complex it is, etc. effect it. Normally refund checks take a 4-6 week process. Electronic deposits, are faster. When you say "file late", that is generally interpreted as in after 4/15, although perhaps you really mean late in the season. Yes, most returns are filed late in the season and that can (comparatively) delay processing time a bit. You actually must pay on time - before 4/15. If your calculation shows that you are overpaid at that time, just like paying, you can still claim your overpayment at that time. The filing of the entire correctly calculated return can be put on extension, basically with no justification needed. Note that you do not have the option of e-filing or receiving your refund electronically if you file late (late being defined as even after the extension date). So if you are "late", you have to wait for a paper check.