Year end is approaching and CRA is preparing to issue tax slips for 2020 year. As CERB is a taxable benefit, prior to issuing the tax slips, CRA sent letters to people who in their view are potentially ineligible for CERB. CRA likely used an algorythm to identify people who received CERB but may not meet the requirements.
For example - you could receive the letter,
If 2019 return wasn't filed, then CRA don't have the information to determine eligibility.
Or if there was less than $5,000 in income, reported in certain income fields in 2019. You may still be eligible if you earned at least $5,000 in 2020, prior to the application. CRA simply don't have this information until you file your 2020 return.
Or the income reported and lost due to COVID is not one that qualifies as eligible income to lose (for example rental income, pension income, employment insurance income etc. Rule of thumb - actively earned income had to be lost.
Common mistakes that would make you ineligible:
1. Net business income needs to have at least $5,000, not gross business income
2. Rental/investment income is not a qualifying income to lose to be able to apply for CERB
Please note however the wording of the letter is general. It is not concluding that you are not eligible. And it does not ask you to return the money because CRA determined that you are not eligible. The letter is asking you to re-review your eligibility. They are listing the criteria for eligibility in the letter. And only if determined that you were not eligible, you need to return the money.
Hope this clarifies and helps you to stop losing sleep as long as you meet the eligibility criteria.