| Subject | English | Welsh |
| comp., MS | backup and restore | creu copi wrth gefn ac adfer (The process of maintaining backup files and putting them back onto the source medium if necessary) |
| comp., MS | backup file | ffeil wrth gefn (A duplicate of a program, a disk, or data, made either for archiving purposes or for safeguarding files) |
| comp., MS | backup withholding | dal wrth gefn (An IRS tax rule in the United States that requires notified payers to withhold a set percentage from payments made to payees who cannot be identified due to missing or incorrect taxpayer identification numbers on tax forms) |