Accountant (letter) for sole trader - EEA FP application

[abraCadabra]

Please help, I am getting confused regarding requirements for an accountant providing supporting letter for my EEA Family Permit application.

My husband is a self-employed subcontractor, registered as a sole trader, his contractor deducts 20% according to CIS - construction industry scheme.

My husband is using a bookkeeper to do his annual self-assessment/tax return. His calculations are not complicated at all. This bookkeeper is an "agent" in HMRC online system for my husband.

As evidence of my husband's self-employement in UK we are going to ask the bookkeeper to print his most recent tax return calculation and a statement of account SA 300 or SA 302.

Also, the bookkeeper will provide a letter explaining that they are acting as agent for my husband's tax matters with HMRC.

I am confused about whether under EEA rules my husband is supposed to hire a CHARTERED accountant. Because, as per UK immigration rules, they are clear that the accountant must be chartered.

I have looked up his bookkeeper in various accountants registers, and could not find them. BUT it is a private limited company, all legal registered business, nature of business - 69202 - Bookkeeping activities.

My husband is not earning too much to afford a chartered accountant, and legally is not required to have them, as far as I understand?

So my question is: as I am applying for an EEA Family Permit, can we submit a supporting letter from his bookkeeper? Or... do we have to comply with UK immigration rules and only provide something from a chartered accountant?