| Document and Entity Information | Feb. 02, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Feb. 2, 2021 |
| Entity Registrant Name | Bill.com Holdings, Inc. |
| Entity Central Index Key | 0001786352 |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
| Entity File Number | 001-39149 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 83-2661725 |
| Entity Address, Address Line One | 6220 America Center Drive, Suite 100 |
| Entity Address, City or Town | San Jose |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 95002 |
| City Area Code | (650) |
| Local Phone Number | 621-7700 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $0.00001 |
| Trading Symbol | BILL |
| Security Exchange Name | NYSE |
