| Document and Entity Information | Nov. 23, 2020 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001786352 |
| Document Type | 8-K |
| Document Period End Date | Nov. 23, 2020 |
| Entity Registrant Name | Bill.com Holdings, Inc. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-39149 |
| Entity Tax Identification Number | 83-2661725 |
| Entity Address, Address Line One | 1800 Embarcadero Road |
| Entity Address, City or Town | Palo Alto |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 94303 |
| 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 |
| Security 12b Title | Common Stock, par value $0.00001 |
| Trading Symbol | BILL |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
